The present disclosure relates to an earth leakage circuit breaker and a method for controlling the same. The earth leakage breaker includes a zero-phase current detection unit for detecting a zero-phase current generated in a zero current transformer formed in three-phase electrical lines; a voltage detection unit for detecting a voltage from each of the two electrical lines; a trip unit for tripping contact points between the two electrical lines and a single-phase load when a trip signal is inputted; and a control unit which, when the zero-phase current is detected by the zero-phase current detection unit, detects an electrical line in which the voltage has dropped by a predetermined level or more, and generates and outputs the trip signal to the trip unit when the electrical line in which the voltage has dropped by a predetermined level or more exists.