The invention provides a tester used for testing a leakage circuit breaker. The tester comprises a box body, an operation side, and a cover plate which can be buckled on the operation side. The operation side is divided into a low voltage operation area and a high voltage operation area. A liquid crystal display screen and an input part are in the low voltage operation area. A test line access terminal, a test power supply parameter display screen, an emergency power off button, an external power supply terminal, an alarm lamp and a heat dissipation air duct inlet are in the high voltage operation area. A handle is arranged on the box body of the tester used for testing the leakage circuit breaker. The other side, which is opposite to the operation side, of the tester used for testing the leakage circuit breaker is a back side, wherein the back side is used for generating overvoltage and overcurrent to test an accessed circuit breaker and testing voltage and/or current parameter state of the circuit breaker.