Provided is a radio communication base station device capable of suppressing degradation of a signal error ratio characteristic for a mobile station in the vicinity of the cell center when a plurality of signals whose transmission power is to be controlled are frequency-multiplexed or code-multiplexed. In the device (100), a classification unit (118) classifies a plurality of DPCCH according to the MCS of SCCH into a plurality of groups based on the transmission power intensity. A spread code is allocated for each DPCCH according to the classification result. A spread code for spreading a response signal (ACK signal/NACK signal) is instructed to spread units (103-1 to 103-n). The spread units (103-1 to 103-n) spread the response signal by the spread code instructed from the classification unit (118). According to the classification result in the classification unit (118), a mapping unit (104) maps the response signal after the spread to one of the subcarriers constituting the OFDM symbol.