PURPOSE: To provide the analog/digital (A/D) converter which can suppress influences upon a sampling value even when analog signals are varied by noise while sampling the analog signals.

CONSTITUTION: An input terminal 1 is connected through a first switch 3 to a first capacitor 2, and a smoothing circuit 17 composed of plural sample/hold circuits 18, 19 and 20 is connected between the input terminal 1 and the first switch 3. The output of this smoothing circuit 17 is compared with the voltage of a reference voltage generating circuit 4 so as to generate digital outputs at a high level or a low level.