A sliding device includes a fixed rail, a movable rail, a lock plate, a spring member, and a fixing structure. The lock plate is displaced between a locking position where the lock plate engages with the fixed rail and restricts slide of the movable rail and a non-locking position where the restriction of slide is released. The spring member exerts an elastic force to maintain the lock plate in the locking position. The fixing structure includes a tapered portion of the spring member and a press spring portion that presses the tapered portion toward a hole of the movable rail.