A backup method of applications of a portable cellular phone is provided which is capable of preventing the applications from being copied by a person being not an owner of the portable cellular phone.The application of the portable cellular phone to be backed up is saved in the backup device and, when the application saved in the backup device is used as backup data for the portable cellular phone, a manufacture serial number and/or a phone number of the portable cellular phone are compared and, only when these numbers match each other, the application for the backup is copied in the portable cellular phone.