A portable information system having an information registration function achieves reduction in manufacturing cost and power consumption. By connecting portable information equipment (1) and a battery charger (10) to be chargeable, signal transmission becomes possible between a micro controller (2) in the portable information equipment (1) and a micro controller (11) in the battery charger (10). Under the control of the micro controllers (2, 11), information management operation is automatically performed during charging. The operation includes backup processing in which personal information stored in a storage portion (3) in the portable information equipment (1) is transferred to a storage portion (12) in the battery charger (10) as backup information, and restore processing in which the backup information stored in the storage portion (12) is transferred to the storage portion (3) as the personal information.