The invention provides a portable on-off tester which comprises a first probe and a second probe, and the front end of the first probe and the front end of the second probe are each provided with a probe head. An on-off indicating lamp, a control switch and a power supply are arranged on the first probe, wherein the on-off indicating lamp and the control switch are positioned on the outer side wall of the first probe, and the power supply is fixedly arranged on the tail end of the first probe through an end cap. A testing lead is arranged between the first probe and the second probe, and one end of the testing lead is connected with one end of the power supply through a holddown device. The portable on-off tester has a small integral structure and is easy to operate. The portable on-off tester can be flexibly used in a narrow test space. The on-off indicating lamp arranged on the first probe allows a test worker to more conveniently determine the on-off of a tested line.