A sliding device for a vehicle comprises a lock member received and attached within a section area of one of relatively movable first and second rails for locking the relative movement between the first and second rails; and a manipulation lever provided for moving the lock member to permit the relative movement between the first and second rails. A movement permitting portion is formed on at at least one of the lock member and the rail attaching the lock member so that the relative movement between the lock member and the rail attaching the lock member in the rail axis direction is allowed with the lock member locking the relative movement. Further, a movement restraining portion is formed on the rail attaching the lock member to restrain the movement in a lock release direction of the lock member after the relative movement at the movement permitting portion.