A system administrator of a wireless LAN 100 manipulates a personal computer PC1 to change a WEP key. The personal computer PC1 authenticates a memory card MC as genuine under management of the system administrator. In the case of the authenticated memory card MC, changed setting information, as well as a previous WEP key before the change of the setting information, is written into the memory card MC. The system administrator then inserts this memory card MC into a memory card slot of a printer PRT1. The printer PRT1 authenticates the memory card MC as genuine under management of the system administrator. In the case of the authenticated memory card MC, the setting information is updated. This arrangement effectively relieves the user's workload in setting wireless communication devices, while ensuring the sufficiently high security.