A touch sensor becomes an operation enable state in which an operation state can be detected, when predetermined voltage is applied. A touch sensor control unit switches the touch sensor to an operation detection enable state by raising the voltage to a predetermined voltage level gradually and performing predetermined calibration when detecting an activation permission request of the touch sensor in a no-voltage applied state of the touch sensor, and switches the touch sensor to an operation detection disable state in which an operation state of the touch sensor cannot be detected by lowering voltage gradually to the no-voltage applied state. And, when detecting the activation permission request of the touch sensor during switching to the operation detection disable state, the touch sensor control unit switches the touch sensor to the operation detection enable state, after the switching operation to the operation detection disable state is completed.