A recording material feed cassette includes first and second cassette portions. The second cassette portion is assembled so as to be capable of extending/retracting relative to the first cassette portion and, along with the first cassette portion, contains a recording material. A locking mechanism fixes the position of the second cassette portion relative to the first cassette portion. The locking mechanism has a lock portion capable of moving in a first direction that is orthogonal to the extension/retraction direction so as to take on a locked position and an unlocked position, an operation portion that is capable of moving in a second direction that follows the extension/retraction direction, and a connection portion that connects the lock portion and the operation portion and that is capable of deforming as a result of the movement of the lock portion in the first direction.