A base station includes: means for deciding scheduling information for allocating at least one resource block for a communication terminal having a preferable channel state according to channel state information reported from a communication terminal; means for encoding and modulating a control channel including an unspecified control channel decoded by an unspecified communication terminal and aspecific control channel decoded by a specified communication terminal for which at least one resource block is allocated for each unspecified control channel corresponding to each communication terminal; multiplexing means for time-multiplexing theunspecified control channel and the specific control channel according to the scheduling information; and means for transmitting the output signal from the multiplexing means by the multi-carrier method.