A ground fault detection apparatus (32) for detecting a ground fault of a safety chain (10b; 10c; 10d), in particular a safety chain (10b; 10c; 10d) of a people conveyor, comprises: a supply line current monitoring unit (26), which is configured for measuring a current flowing into the safety chain (10b; 10c; 10d) and providing a first signal indicative of the amount of current flowing into the safety chain (10b; 10c; 10d); a return line current monitoring unit (28), which is configured for measuring a current flowing out of the safety chain (10b; 10c; 10d) and providing a second signal indicative of the amount of current flowing out of the safety chain (10b; 10c; 10d); and a comparison unit (30), which is configured for comparing the first and second signals and issuing an alarm signal in case the difference between the first and second signals exceeds a predetermined limit.