Provided are a base station, a terminal, a band allocation method, and a downlink data communication method with which bands can be efficiently allocated. In a base station in which a plurality of unit bands can be allocated to a single communication, when a data receiver acquires terminal capability information transmitted by a terminal in the initial access unit band and the bandwidth available for communication indicated by the terminal capability information can accommodate a plurality of unit bands, a unit band group which includes the initial access unit band as well as the unit bands adjacent thereto is allocated to the terminal, and a communication band movement indication, which indicates the movement of the center frequency in the communication band of the terminal toward the center frequency in the unit band group, is transmitted to the terminal using the initial access unit band.