A holder is removable from a seatback frame. The seatback frame has a back plate, a top plate extending from an upper portion of the back plate toward a front side, and a fixing plate provided below the top plate and extending from the back plate toward the front side. The top plate has two insertion holes into which two holders can be inserted from above. The fixing plate is configured so as to be able to fix the end portions of the two holders inserted through the insertion holes of the top plate.