A key switch used for a keyboard incorporated as an input device in electronic equipment. The key switch includes a support plate; a key top arranged above the support plate; a pair of link members interlocked to each other to support the key top above the support plate and direct the key top in a vertical direction; and a switch mechanism capable of opening and closing a contact section of an electric circuit in accordance with a vertical movement of the key top. The switch mechanism includes a membrane switch sheet carrying the contact section at a position corresponding to the key top and placed on the support plate. Each of the link members includes a sliding part slidably engaged with the support plate. The membrane switch sheet is provided with a through-hole in a region where the sliding part of each link member is engaged with the support plate, the sliding part of the link member being slidably placed on the support plate through the through-hole in the membrane switch sheet.