A charging monitor has: a switch that is disposed between a load section having a storage battery and an external AC power supply supplying a current to the load section via a plurality of lines and interrupts the supply of the current from the external AC power supply to the load section; a current detection circuit that outputs a detection signal corresponding to a difference in level between currents flowing through the lines; a suppression circuit that suppresses a DC component contained in the detection signal; a filter circuit that filters a plurality of frequency components contained in the detection signal so that attenuation increases as a frequency becomes high; a rectifier smoothing circuit that rectifies and smoothens an output signal obtained when the detection signal passes through the filter circuit and the suppression circuit; and an electric leakage determination circuit that detects an electric leakage and shuts off the switch when the level of the signal smoothened by the rectifier smoothing circuit exceeds a preset reference level.
