An appearance of other mobile wireless station within a communication area of a second wireless communication system of a main mobile wireless station when the main mobile wireless station is in the communication area of a wireless base station of the first wireless communication system, is automatically detected. Communications with other mobile wireless station are autonomously started by a second wireless communication system and communications with the wireless base station are performed by the first wireless communication system. Communication content from the wireless base station of the first wireless communication system and communication content from the other mobile wireless station of the second wireless communication system are mutually relayed. The relay control is terminated when the other mobile wireless station moves outside the communication area of the second wireless communication system of the main mobile wireless station.