A wireless communication system capable of saving time for mutual data communication in a sniff mode. The wireless communication system has: a master apparatus for calculating a sniff parameter including a time of a sniff period capable of performing the communication by allowing a corresponding device to commonly have the time in the sniff mode, when a communication mode for a mutual data communication by a user is selected to be operated in the sniff mode; and a sniff slave apparatus for performing the mutual data communication with the master apparatus by commonly having a corresponding time calculated in accordance with the sniff parameter. At this time, the sniff parameter includes at least one among a cyclic information, an allocated time information of the sniff period, and a start time information in which the master apparatus communicates with the sniff slave apparatus operated in the sniff mode.