One example of a sliding device that can sufficiently reduce a separation phenomenon is disclosed. The sliding device includes a fixed rail, a movable rail, a fixed-side hook, an engagement hook, and a reinforcing hook. The fixed rail is configured to be fixed to a vehicle. To the movable rail, the seat body is attachable. The movable rail is slidable with respect to the fixed rail. The fixed-side hook is configured to be fixed to the vehicle. The engagement hook is provided to the movable rail. The engagement hook is engageable with the fixed-side hook, and is formed by a first plate material curved approximately into a letter J or U shape. The reinforcing hook overlaps with the engagement hook in a thickness direction of the first plate material. The reinforcing hook is formed by a second plate material curved approximately into a letter J or U shape.