To allow a signal having an arbitrary waveform up to a high frequency area to be generated by expanding a frequency band of the signal to be generated while using a sampling frequency of a relatively low frequency.

A complex spectrum in a frequency area in which a target signal is subjected to discrete Fourier transform is divided into P sets of signal components. They are subjected to split processing by distributing them to P signal modules SG1, SG2, SG3to SGPoperating at a low sampling clock, and the respective outputs are combined to generate an arbitrary signal. Each signal module subjects the distributed signal component to inverse discrete transform by an inverse discrete Fourier transformer 10, and the inverse discrete Fourier transform output is up-converted by a quadrature modulator 17, with respect to a high-frequency component having difficulties in digital signal processing. Accordingly, each of the signal modules SG2, SG3to SGPis operated with a low-speed clock inversely proportional to a parallel number P.

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