A rectifier (107) includes a rectifying MOSFET (101) that performs synchronous rectification, a control circuit (106) that inputs a voltage across a pair of a positive-side main terminal TK and a negative-side main terminal TA of the rectifying MOSFET (101) to determine an ON or OFF state of the rectifying MOSFET (101) based on the inputted voltage, and a capacitor (104) that supplies power to the control circuit (106). The control circuit (106) includes a blocking circuit (105) that inputs the voltage across the pair of main terminals of the rectifying MOSFET (101), to block power supply to the control circuit (106) when the inputted voltage across the pair of main terminals is higher than or equal to a first voltage, and to unblock power supply to the control circuit (106) when the inputted voltage across the pair of main terminals is lower than the first voltage.