PURPOSE: To change an output waveform at real time and to output the changed waveform synchronously with an external signal.

CONSTITUTION: An analog output device for successively writing digital signals sampled and stored in a memory 24 in a digital/analog conversion part 20, converting the written digital signal into analog voltages by using an external signal as a reference and outputting the analog voltages is provided with a synchronism control means 21 for inputting an external signal into the conversion part 20, converting and outputting the written digital signals and then turning on an identification flag 22 and a writing means 23 for monitoring the identification flag 22, reading out the succeeding digital signal from the memory 24 when the identification flag is ON, writing the read signal in the conversion part 20 and then turning off the identification flag 22.