A rectifier includes a rectification MOSFET that performs rectification, a comparator formed by connecting a drain of the rectification MOSFET to a non-inverting input terminal and a source to an inverting input terminal, and a control circuit that performs an on/off control of the rectification MOSFET using an output of the comparator. The control circuit includes a shut-off MOSFET that disconnects a drain of the rectification MOSFET and a non-inverting input terminal of the comparator from each other, and a shut-off circuit that turns off the shut-off MOSFET to electrically disconnect the drain of the rectification MOSFET and the non-inverting input terminal of the comparator from each other when the drain voltage of the rectification MOSFET is equal to or higher than a predetermined first voltage.