To provide a three-phase ground fault interrupter interrupting leakage even with one phase open, causing no damage such as burnout even when reverse-connected and allowing high-speed interruption.

The power is supplied via a three-phase full-wave rectifier circuit 10 to a leakage determination circuit 7 and a trip coil 4 receives operating currents from two different phases of an electric circuit 1. A first thyristor 9 turned on under the control of the leakage determination circuit 7 is disposed on a common current supply passage 12. A second thyristor 14 and a third thyristor 15 turned on in cooperation with turning-on of the first thyristor 9 are disposed on two-phase-branched current supply passages 12a, 12b of the electric circuit 1.