PURPOSE: To simplify constitution by adding control information to set the fluctuation part of an oscillation frequency, a constant to set the central frequency of the oscillation frequency and latch feedback information, latching in accordance with a clock signal, supplying them to an adding means as the latch feedback information and outputting a desired waveform signal in accordance with a latch output.

CONSTITUTION: In adding means 3, 6 control information KV to set a fluctuation part KV/N.f0 of an oscillation frequency (f), a constant M to set a central frequency M/Nf0 of the oscillation frequency (f) and latch feedback information Y are added. Namely, a value Y, control information KM and the constant M latched by a time T=1/f0 earlier are added by an adder 6 with modulo N. An added value Y' is expressed by (Y+KV+M)mod N. An adding output Y' is latched to an information holding means 7, a latch output Y is fed back to adding means 3, 6, supplied to a waveform converting means 9, and a desired waveform signal is outputted in accordance with the latch output by the waveform converting means 9. Thus, constitution is simplified.