To provide a DDS (Direct Digital Synthesizer) signal generator allowing a comparatively small waveform memory in size and acted by the result of arithmetic operation based on a strictness expression independent of an approximation expression.

The DDS signal generator is composed of: the waveform memory applying table formation to the trigonometric function of a waveform arithmetic expression for storage; a phase arithmetic and logic unit outputting phase data as an address for reading the desired trigonometric function from the waveform memory; a waveform arithmetic operation section executing arithmetic operation based on the waveform arithmetic expression by using the trigonometric function read from the waveform memory; and a D/A (Digital/Analog) converter converting the arithmetic output of the waveform arithmetic operation section into an analog waveform signal.