A radio communication apparatus receives control information on one or more control channel elements (CCEs) with consecutive CCE number(s). The radio communication apparatus first-spreads a response signal with a sequence defined by a cyclic shift value that is determined among a plurality of cyclic shift values from an index of physical uplink control channel (PUCCH), which is associated with a first CCE number of the one or more CCEs, and second-spreads the first-spread response signal with an orthogonal sequence that is determined among a plurality of orthogonal sequences from the index. One of cyclic shift values used for an orthogonal sequence is determined from an index of the PUCCH, which is associated with an odd CCE number, and another one of the cyclic shift values used for the same orthogonal sequence is determined from an index of the PUCCH, which is associated with an even CCE number.