A POS terminal, includes a battery box having a box-side commercial power source circuit to supply power from a commercial power source; a battery charge circuit to charge batteries by power supplied from the box-side commercial power source circuit; a battery discharge circuit to discharge the batteries to a POS terminal main body side; and a charge and discharge changeover switch which connects a battery discharge circuit to the batteries to cause the batteries to be discharged when the battery box is attached to a POS terminal main body, and connects a battery charge circuit to the batteries to cause the batteries to be charged when the battery box is detached from the POS terminal main body.