An integration type A/D converter has two sets of integration type A/D converter sections which can be periodically switched over at a predetermined period, with one converter section integrating an input signal to give an integral output voltage and another converter section performing A/D conversion of the integral output voltage. Further, use is made of a residual time interval in the period of A/D conversion, for the integration of the ground voltage and a reference voltage and for A/D conversions of the integrated voltages. The inventive A/D converter permits accurate measurement of continuous integral values of a given input signal.