PURPOSE: To generate a modulated wave digitally by converting the pulse width modulated wave of a reference waveform into digital value indicated by truth values "1" and "0" corresponding to the level of the modulated wave, storing the digital value in a memory and reading out information in each address of the memory.

CONSTITUTION: A pulse width-modulated value is divided into n bits, the truth values "1" and "0" of respective bits are successively stored in respective addresses a1∼an of an ROM1 and the addresses a1∼an are successively and repeatedly specified by an address specifying circuit 2 provided with a clock signal generator 4 and an address counter 5 counting up cloc signals. Thus, pulse width modulated waves are repeatedly outputted from the ROM1 and sine waves are demodulated and outputted repeatedly from an LPF3. In this device, the frequency of demodulated waves outputted from the LPF3 can be changed only by changing the frequency of clock signals inputted to the counter 5 and the modulated waves can be digitally generated from the IC circuit, so that the structure is extremely simplified.