Disclosed is a wireless communication base station device which can prevent unnecessary HARQ retransmissions when a terminal is using a plurality of unit bands, even when the unit band through which data is transmitted differs from the unit band through which a PDCCH, to which the resource allocation information of said data is allocated, is transmitted. In this device, a control unit (102) generates, for each of a plurality of downlink unit bands, CFI information, which indicates the number of symbols used in a control channel to which resource allocation information of downlink data to be sent to the terminal has been allocated, with respect to the terminal, which communicates using a plurality of downlink unit bands; a scrambling unit (105) scrambles a control channel in a sequence corresponding to CFI information of downlink bands used in the allocation of downlink data, when, in a plurality of downlink unit bands, the downlink unit band used in the allocation of downlink data and the downlink unit band which transmits control channels to which resource allocation information has been allocated differ from one another.