A key input device is provided. The key input device includes a pressure key having a pressing surface, a pressure sensor formed on an opposite surface side of the pressing surface of the pressure key, a flexible member formed on a side portion of the pressure key, a vibration actuator attached to the flexible member, and a controller for controlling the vibration actuator according to a pressure detected by the pressure sensor, or includes a touch key having a touch surface, a touch sensor formed on an opposite surface side of the touch surface of the touch key, a flexible member formed on a side portion of the touch key, a vibration actuator attached to the flexible member, and a controller for controlling the vibration actuator according to a touch detected by the touch sensor.