In an automobile having a seat cushion and a seat back that can be stored in a non-use position located in the upper part of a vehicle interior, the seat back can be stored in the non-use position easily even when the seat back stops at any position immediately before the non-use position thereof when the seat back is lifted up to the non-use position. A guide face is formed on a locking member. The guide face brings an engaging concave portion of the locking member into engagement with a striker while being in sliding contact with the striker when a handle arm provided on the seat back is rotated from the use position to the storage position thereof to rotate the locking member from the lock releasing position toward the locking position thereof, in a situation where the seat back stops upon reaching any position immediately before the non-use position thereof.