A transmitter includes a time/frequency-domain converter (12) that converts a time-domain data signal to a frequency-domain data signal of a fixed number (N DFT ); a subcarrier llocator (14) that allocates the obtained frequency-domain data signal to any of (N IFFT ) subcarriers, the number of which exceeds the fixed number (N DFT ), the subcarriers being allocated in a predetermined transmission frequency Band; and a controller (18) that controls the subcarrier allocator (14) to allocate signals other than the data signal to subcarriers in an idle band to which the data signal is not allocated. By this, without the need for a plurality of time/frequency-domain conversion circuits with a large size, such as DFTs, frequency utilization efficiency (data transmission efficiency) is improved.