A slave station which transmits/receives signals to/from a master station, the slave station includes: a transmitting unit and receiving unit for transmitting/receiving signals regarding the master station; a storing unit; an input unit; wherein under a control by a control unit, the transmitting unit transmits a transmission request for transmitting multicast data to the master station in accordance with a timing of power-on or an input by the input unit; the receiving unit receives information of a number of times of transmission for requested multicast data from the master station and stores the number in the storing unit; and after receiving the multicast data the number of times of transmission stored in the storing unit, the control unit determines presence of absence of lacking data which have not been received and, transmits a retransmission request for requesting the lacking data in a case of presence the lacking data.