The embodiment of the utility model provides a step voltage detector which comprises a testing contact, a hand-contact electrode, a shell, a triode, a current-limiting resistor, a neon tube, a first buzzer, a shunt resistor, a triode load resistor, a first switch and a direct-current power supply, wherein the testing contact is connected with a base electrode of the triode; one end of the shunt resistor is connected with the base electrode of the triode, and the other end of the shunt resistor is connected with an anode of the direct-current power supply by the first switch; one end of the triode load resistor is connected with a collector of the triode, and the other end of the triode load resistor is connected with the first switch; the current-limiting resistor, the neon tube and the first buzzer are connected in series and then connected between the collector and an emitter of the triode; the hand-contact electrode is connected with the emitter of the triode; and a cathode of the direct-current power supply is connected with the emitter of the triode. The step voltage detector can effectively detect the existence of step voltage, give an alarm timely beyond safety distance, and prevent operators from getting close to danger areas, therefore, accidents of electric shock to the operators can be avoided.