A dual slope A/D converter with a zero compensation circuit includes a single power source, an integrator, and a MOS switch constituting the zero compensation circuit and adapted to apply an output voltage to the noninverting input terminal of an operational amplifier constituting the integrator for a zero compensation duration. The A/D converter further includes an amplifier and a MOS transistor with the same characteristics as those of the MOS switch. The gate and source of the MOS transistor are connected to the noninverting input terminal of the operational amplifier. The amplifier doubles a voltage at the noninverting input terminal of the operational amplifier. A doubled voltage is applied to the drain of the MOS transistor.