A diode detection circuit is capable of obtaining an ideal rectification voltage even the case of a minute input high-frequency voltage. The circuit includes a first diode that accepts an AC signal; a first parallel circuit consisting of a resistor and a capacitor, the first parallel circuit accepting a detection output from the first diode; a first operational amplifier having a positive input terminal that accepts a charging voltage for the capacitor of the first parallel circuit; a second diode that accepts an output from the first operational amplifier; a first switching circuit consisting of a first switch and an oscillator, the first switching circuit providing a control of the ratio of conduction to non-conduction of the first and second diodes; a second parallel circuit consisting of a resistor and a capacitor, the second parallel circuit accepting an output from the first switching circuit.