To prevent the malfunction of a protective circuit and, to improve the protection stability of the circuit at the same time.

In a battery charger, provided with a voltage detecting circuit 3 which detects the voltage across the terminals of a charging route containing a secondary battery B, a charging-control circuit 2 having such an output characteristic that the output voltage of the circuit 2 becomes higher that the detected voltage of the circuit 3, when the charging current of the battery B becomes larger by correcting at least the voltage drop caused by the other resistance component than the battery B in the route, and an overvoltage protective circuit 10 which interrupts the charging of the battery B when the detected voltage of the circuit 3 exceeds a set value, the set voltage is set nearly proportional to the output characteristic of the circuit 2.