diff --git a/domain/comment.go b/domain/comment.go
new file mode 100644
index 0000000..c7fc18c
--- /dev/null
+++ b/domain/comment.go
@@ -0,0 +1,17 @@
+package domain
+
+import "time"
+
+type Comment struct {
+	ID        int
+	ItemID    int
+	UserID    string
+	Text      string
+	CreatedAt time.Time
+	UpdatedAt time.Time
+	DeletedAt *time.Time
+}
+
+type CommentRepository interface {
+	Create(comment *Comment) error
+}
diff --git a/domain/errors.go b/domain/errors.go
index 686f9c4..bb43cd9 100644
--- a/domain/errors.go
+++ b/domain/errors.go
@@ -3,7 +3,8 @@ package domain
 import "errors"
 
 var (
-	ErrNotFound        = errors.New("not found")
-	ErrInvalidFileType = errors.New("invalid file type: only JPEG and PNG are allowed")
-	ErrFileTooLarge    = errors.New("file too large: max size is 3MB")
+	ErrNotFound         = errors.New("not found")
+	ErrInvalidFileType  = errors.New("invalid file type: only JPEG and PNG are allowed")
+	ErrFileTooLarge     = errors.New("file too large: max size is 3MB")
+	ErrCommentTextEmpty = errors.New("comment text cannot be empty")
 )
diff --git a/handler/comment.go b/handler/comment.go
new file mode 100644
index 0000000..5ffbecf
--- /dev/null
+++ b/handler/comment.go
@@ -0,0 +1,44 @@
+package handler
+
+import (
+	"net/http"
+
+	"github.com/labstack/echo/v4"
+	"github.com/traPtitech/booQ-v3/domain"
+	"github.com/traPtitech/booQ-v3/handler/openapi"
+)
+
+func (h *handler) PostComment(ctx echo.Context, itemId openapi.ItemIdInPath) error {
+
+	var req openapi.PostComment
+	if err := ctx.Bind(&req); err != nil {
+		return ctx.JSON(http.StatusBadRequest, err)
+	}
+
+	// TODO: ミドルウェアからユーザーidを取得するように
+	userId := "test-user-id"
+
+	comment, err := h.cu.CreateComment(itemId, userId, req.Text)
+	if err != nil {
+		if err == domain.ErrItemNotFound {
+			// Itemがないとき
+			return ctx.JSON(http.StatusNotFound, "item not found")
+		} else if err == domain.ErrCommentTextEmpty {
+			// 投稿されたコメントが空の時
+			return ctx.JSON(http.StatusBadRequest, "comment text is empty")
+		}
+
+		return ctx.JSON(http.StatusInternalServerError, err)
+	}
+
+	res := openapi.Comment{
+		Id:        &comment.ID,
+		ItemId:    &comment.ItemID,
+		UserId:    &comment.UserID,
+		Text:      comment.Text,
+		CreatedAt: &comment.CreatedAt,
+		UpdatedAt: &comment.UpdatedAt,
+	}
+
+	return ctx.JSON(http.StatusCreated, res)
+}
diff --git a/handler/handler.go b/handler/handler.go
index ddd65a8..ad28b02 100644
--- a/handler/handler.go
+++ b/handler/handler.go
@@ -8,13 +8,15 @@ import (
 
 type handler struct {
 	iu usecase.ItemUseCase
+	cu usecase.CommentUsecase
 	fu usecase.FileUseCase
 }
 
-func NewHandler(iu usecase.ItemUseCase, fu usecase.FileUseCase) openapi.ServerInterface {
+func NewHandler(iu usecase.ItemUseCase, cu usecase.CommentUsecase, fu usecase.FileUseCase) openapi.ServerInterface {
 	return &handler{
 		iu: iu,
 		fu: fu,
+		cu: cu,
 	}
 }
 
@@ -48,11 +50,6 @@ func (h *handler) PostBorrowEquipmentReturn(ctx echo.Context, itemId openapi.Ite
 	panic("implement me")
 }
 
-func (h *handler) PostComment(ctx echo.Context, itemId openapi.ItemIdInPath) error {
-	//TODO implement me
-	panic("implement me")
-}
-
 func (h *handler) RemoveLike(ctx echo.Context, itemId openapi.ItemIdInPath) error {
 	//TODO implement me
 	panic("implement me")
diff --git a/main.go b/main.go
index 9f5a3e1..cd78009 100644
--- a/main.go
+++ b/main.go
@@ -37,6 +37,7 @@ func main() {
 
 	// Repository
 	itemRepo := repository.NewItemRepository(db)
+	commentRepo := repository.NewCommentRepository(db)
 	fileRepo := repository.NewFileRepository(db)
 
 	// Storage
@@ -44,10 +45,11 @@ func main() {
 
 	// UseCase
 	itemUseCase := usecase.NewItemUseCase(itemRepo)
+	commentUsecase := usecase.NewCommentUsecase(commentRepo, itemRepo)
 	fileUseCase := usecase.NewFileUseCase(fileRepo, fileStorage)
 
 	// Handler
-	h := handler.NewHandler(itemUseCase, fileUseCase)
+	h := handler.NewHandler(itemUseCase, commentUsecase, fileUseCase)
 	openapi.RegisterHandlers(e, h)
 
 	e.Logger.Fatal(e.Start(":3001"))
diff --git a/repository/comment.go b/repository/comment.go
new file mode 100644
index 0000000..894beee
--- /dev/null
+++ b/repository/comment.go
@@ -0,0 +1,43 @@
+package repository
+
+import (
+	"time"
+
+	"github.com/traPtitech/booQ-v3/domain"
+	"gorm.io/gorm"
+)
+
+type comment struct {
+	GormModel        // ID, CreatedAt, UpdatedAt
+	ItemID    int    `gorm:"not null"`
+	UserID    string `gorm:"type:varchar(32);not null"`
+	Text      string `gorm:"column:comment;type:text;not null"`
+	DeletedAt *time.Time
+}
+
+type commentRepository struct {
+	db *gorm.DB
+}
+
+func NewCommentRepository(db *gorm.DB) domain.CommentRepository {
+	return &commentRepository{db: db}
+}
+
+func (r *commentRepository) Create(c *domain.Comment) error {
+	newComment := &comment{
+		ItemID: c.ItemID,
+		UserID: c.UserID,
+		Text:   c.Text,
+	}
+
+	if err := r.db.Create(newComment).Error; err != nil {
+		return err
+	}
+
+	c.ID = newComment.ID
+	c.CreatedAt = newComment.CreatedAt
+	c.UpdatedAt = newComment.UpdatedAt
+	c.DeletedAt = newComment.DeletedAt
+
+	return nil
+}
diff --git a/repository/db.go b/repository/db.go
index 8194669..f6f1b6d 100644
--- a/repository/db.go
+++ b/repository/db.go
@@ -14,6 +14,7 @@ import (
 var allTables = []interface{}{
 	item{},
 	file{},
+	comment{},
 }
 
 type GormModel struct {
diff --git a/usecase/comment.go b/usecase/comment.go
new file mode 100644
index 0000000..f01dc44
--- /dev/null
+++ b/usecase/comment.go
@@ -0,0 +1,53 @@
+package usecase
+
+import (
+	"github.com/traPtitech/booQ-v3/domain"
+)
+
+type CommentUsecase interface {
+	CreateComment(
+		itemID int,
+		userID string,
+		text string,
+	) (
+		*domain.Comment, error,
+	)
+}
+
+type commentUsecase struct {
+	CommentRepo domain.CommentRepository
+	ItemRepo    domain.ItemRepository
+}
+
+func NewCommentUsecase(commentRepo domain.CommentRepository, ItemRepo domain.ItemRepository) CommentUsecase {
+	return &commentUsecase{
+		CommentRepo: commentRepo,
+		ItemRepo:    ItemRepo,
+	}
+}
+
+func (u *commentUsecase) CreateComment(itemId int, userId string, text string) (*domain.Comment, error) {
+
+	_, err := u.ItemRepo.GetByID(itemId)
+
+	if err != nil {
+		return nil, err
+	}
+
+	if text == "" {
+		return nil, domain.ErrCommentTextEmpty
+	}
+
+	comment := &domain.Comment{
+		ItemID: itemId,
+		UserID: userId,
+		Text:   text,
+	}
+
+	err = u.CommentRepo.Create(comment)
+	if err != nil {
+		return nil, err
+	}
+
+	return comment, nil
+}