A base station that suitably controls retransmission in license-free bands. In the base station (100), a transmission unit (107) sends control information pertaining to retransmission requests for response signals for downlink data and a reception unit (108) receives response signals that have been retransmitted on the basis of the control information. The control information identifies one among a plurality of candidate values pertaining to the number of response signals requested for retransmission. The plurality of candidate values are set on the basis of any one of a plurality of grain sizes.