In order to drive a PC and a cam-coder communicating with each other by adopting a Bluetooth technique to carry out mutual authentication processing, the user presses an authentication button of the PC and an authentication button of the cam-coder simultaneously. An authentication program of the PC detects an on time to turn on the authentication button of the PC and an off time to turn off the button. Likewise, an authentication program of the cam-coder detects an on time to turn on the authentication button of the cam-coder and an off time to turn off the button. The detected on and off times are exchanged between the PC and the cam-coder. If a difference between the on times and a difference between the off times are each found to be within a predetermined range, a result of the mutual authentication processing is considered to be positive. In this way, the mutual authentication processing can be carried out with ease.