An OFDM (Orthogonal Frequency Division Multiplexing) modulator of the present invention includes a polar coordinates converter to which real axis data and imaginary axis data output from a discrete inverse Fourier transformer are input. The converter converts the two kinds of input data to amplitude data to phase data. A carrier wave is subjected to phase modulation using the phase data and then input to a power amplifier as an input RF (Radio Frequency) signal. The power amplifier is implemented by a C class power amplifier having inherently high power utilization efficiency. The output level of the power amplifier is controlled in accordance with the amplitude data.