A current monitoring circuit for monitoring a charging/discharging current of a secondary battery that achieves high-precision monitoring and that restricts an increase in the circuit scale. An amplifier amplifies a voltage of a current sense resistor generated by a charging/discharging current under a various amplification degrees. A comparator compares an output voltage of the amplifier with a reference voltage. A controller controls a reference voltage to be supplied to each unit and controls the amplification degree of the amplifier, based on a result of the comparison. An A/D converter A/D converts an output voltage of the amplifier. A numerical-value converter converts a digital value obtained by the conversion of the A/D converter into a numerical value corresponding to a charging/discharging current, under the control of the controller. When an excess current has been detected, a switch is set to a non-conductive state, to thereby disconnect the battery from the external unit.