Provided is a radio communication base station device which can obtain a maximum frequency diversity effect of a downstream line control channel. The device includes: an RB allocation unit (101) which allocates upstream line resource blocks continuous on the frequency axis for respective radio communication mobile stations by the frequency scheduling and generates allocation information indicating which upstream line resource block has been allocated to which radio communication mobile station device; and an arrangement unit (109) which arranges a response signal to the radio communication mobile station device in the downstream line control channels distributed/arranged on the frequency axis while being correlated to the continuous upstream line resource blocks according to the allocation information.