It is possible to provide a radio communication base station device, a radio communication terminal device, and a response signal allocation method which perform D-ACK and P-ACK resource allocation while maintaining a high use efficiency of the upstream line control channel of PUCCH or the like. When a plurality of CCE are allocated upon PDCCH transmission, PUCCH resources corresponding to odd CCE numbers are allocated for D-ACK and PUCCH resources corresponding to even CCE numbers are allocated for P-ACK among a plurality of CCE numbers which can be used.