To provide a slide rail device for simplifying a structure and lightly reciprocating a moving side rail by forming respective rails of a plate-like member such as a steel plate and belt steel in the slide rail device forming either one rail as a fixed side rail and the other rail as a movable slide rail among a first rail and a second rail.

This slide rail device is composed of the first rail 2 having a guide groove 2a in both side edges of the plate-like member, and the second rail 3 having a guide groove 3a in both side edges of the plate-like member. A sphere 4b held by a cage is rotatably arranged in the guide groove of the first rail 2, and the second rail 3 can move via this sphere. A gear 8 driven by an electric motor is arranged on the first rail 2, and the second rail is moved by engaging the gear 8 with a tooth-shaped projection 3b formed on the second rail 3.