This invention is directed to simplify operation to be performed by an operator and allow authentication processing between two apparatuses while each apparatus uses a single wireless communication unit. For this purpose, when an authentication start instruction button is operated, a host apparatus decreases its RF power to set a communication range to about several ten cm. The host transmits an inquiry signal containing verification data and time interval data. A device which has received this inquiry signal transmits an inquiry response signal containing verification data and information for specifying itself at instructed time intervals. The host transmits authentication information only when this inquiry response is received at the set time intervals, the inquiry response contains verification data, the reception signal intensity changes in a predetermined range, and the inquiry response is sent from one device.