An analog multiplexer with an insulated power supply includes: an analog signal transformer receiving an analog signal input in its primary winding via an FET, and ON/OFF driving the FET to generate a pulse with an amplitude of the analog signal in its secondary winding; a drive transformer receiving a drive pulse input in its primary winding via an FET to generate a pulse turning ON/OFF the FET in its secondary winding; an inhibit generation circuit generating an inhibit pulse having a wider pulse width than that of the drive pulse; an AND gate determining a logical product of a continuous pulse from a continuous pulse generation circuit and the inhibit pulse to obtain a power supply pulse train; and a rectifying/smoothing circuit obtaining a direct current voltage corresponding to the power supply pulse train to apply the direct current voltage to the primary winding of the transformer through high resistance.