To provide an earth leakage circuit breaker with sufficiently secured insulation without needing complicated insulating structures or large spatial distances.

An earth leakage circuit breaker 1 is equipped with a residual current transformer ZCT1 for detecting a leak in a main circuit and outputting a signal, a control circuit 2 for detecting the output signal of the residual current transformer ZCT1 and outputting a signal when a leak more than a preset value is detected, a thyristor SCR1 to be turned on by the output signal from the control circuit 2, a trip coil TC1 to be excited by the turning-on of the thyristor SCR1, a coil bobbin 3 formed of a cylindrical body 3A and flange parts 3B, 3C provided on both ends of the cylindrical body 3A and wound with the trip coil TC1, a magnetic coil MC1 for instantaneous tripping concentrically wound on an outer circumference of the trip coil TC1 wound on the coil bobbin 3, a plunger 4 inserted in the cylindrical body 3A of the coil bobbin 3 and operating when the trip coil TC1 or the magnetic coil MC1 is excited, and contacts 5 of the main circuit to be tripped by the operation of the plunger 4. The trip coil TC1 and magnetic coil MC1 are connected so that their polarity is the same.