A modulator generates a modulation signal from an input signal. A serial-parallel converter generates a subcarrier modulation signal from the modulation signal. An inserter inserts a transmission-side data series, generated by multiplying a data series having an autocorrelation property by a predetermined series amplitude coefficient, in a signal for synthesis, generated by multiplying the subcarrier modulation signal by a predetermined signal amplitude coefficient, in such a way that elements in the signal for synthesis and elements in the transmission-side data series are alternately positioned, thereby generating first data. An IFFT unit performs an inverse fast Fourier transformation on the first data. A separator generates a baseband signal based on first half data of an operation result from the IFFT unit. A transmitter generates a transmission signal from the baseband signal, and transmits it to another apparatus via an antenna.