Communication bands are effectively allocated to each communication station under a communication environment of an autonomous distributed type system such as an ad-hoc communication. Each communication station acquires a priority slot with which each communication station itself performs data transmission preferentially at predetermined time intervals, and releases or allocates its own priority slot to other communication station in response to a permission form upper layer of a communication protocol based on a fact that the transmission data is not in a buffer. Thereby, it is able to effectively utilize the communication bands, and to improve a throughput of the whole system.