A wireless communication apparatus capable of minimizing the degradation of the separation characteristic of response signals to be code-multiplexed. In the apparatus, a control part (209) controls both a ZC sequence to be used for the primary spread in a spreading part (214) and a Walsh sequence to be used for the secondary spread in a spreading part (217) according to the associations between sequences and CCEs established in accordance with the probability of using response signal physical-resources corresponding to CCE numbers. The spreading part (214) performs the primary spread of the response signal by use of the ZC sequence established by the control part (209). The spreading part (217) performs the secondary spread of the response signal, to which CP has been added, by use of the Walsh sequence established by the control part (209).