PURPOSE: To obtain an A/D converter circuit with a comparatively small circuit scale and a fast conversion speed by operating plural A/D converters sequentially through time shift and extracting each output in time series.

CONSTITUTION: An analog input voltage VA1 given to an input terminal 1 is inputted to an A/D converter 4, which starts the conversion at a time t. and the conversion operation continues up to a time t3. Furthermore, an analog input voltage VB1 at the input terminal 1 is given to an A/D converter 5, which starts the conversion at a time t2 and continues up to a time t4. Then a multiplexer 8 is subjected to switching control by a clock and an output of a D flip-flop 6 passes at a high level of the clock and an output of a D flip-flop 7 passes at a low level. Thus, the multiplexer 8 provides an output of data A1, A2,... obtained by A/D-converting the input data by the A/D converter 4 or data B1, B2,... obtained by A/D-converting the input data by the A/D converter 5 alternately in time series.