A key switch device capable of preventing a key top from displacing in the horizontal direction when the key top is being depressed, and of minimizing wear and damage to the components thereof. A displacement restricting part, contacting each of a pair of link members, is formed by punching and bending a support plate. Further, on the back side of a trunk of each link member, an engaging portion capable of contacting the displacement restricting part is formed. When the key top is being depressed, the displacement restricting part always contacts the engaging portion, whereby the displacement of the link members in the horizontal direction or the slipping movement of the key top may be prevented.