An A/D converter for driving a plurality of delay units forming a pulse delay circuit by an analog input signal Vin and digitalizing the number of delay units through which a pulse signal passes in the pulse delay circuit at predetermined timings, provided with a plurality of pulse position digitalizing units used for A/D conversion and inputting delay pulses from the delay units of the pulse delay circuit to the pulse position digitalizing units through an inverter group comprised of inverters with different inversion levels (switching threshold level) by different input timings. The digital data obtained by the pulse position digitalizing units are added by an adder.