A key switch unit includes a keycap elongated in a lengthwise direction; a switch mechanism; a supporting plate supporting the switch mechanism; and a key reinforcement mechanism engaging the keycap on its lower side for reinforcement. The key reinforcement mechanism includes a first wire member having a beam part extending over substantially an overall dimension of the keycap in the lengthwise direction; a second wire member having a beam part extending in the lengthwise direction between a region contacting the switch mechanism and a first lengthwise end of the keycap; and a third wire member having a beam part extending in the lengthwise direction between the region and a second lengthwise end of the keycap. The beam parts engage the keycap on its lower side. The first, second, and third wire members have respective end parts turnably supported on the supporting plate.