To extremely reduce damage to a primary battery that is fitted by mistake with an extremely simple circuit.

A charger for charging a plurality of secondary batteries is provided with a fitting part for fitting a plurality of secondary batteries 1 detachably and simultaneously charges the secondary batteries 1 that are fitted to the fitting part. Further, in the charger, a voltage divider resistor 12 is connected in series with a plurality of secondary batteries 1, and the secondary batteries are connected in parallel one another and at the same time are connected to a power supply circuit 9 with output voltage-limiting characteristics for controlling an output voltage to a value that is lower than a set voltage.