When an authentication request is made, processing for the authentication request is executed based on information about a first device even if account information set for a first storage system does not exist. When information is exchanged between a home storage system 10 and an online storage system 18 via the Internet 20, and if account information does not exist due to, for example, replacement with a new device, when making an authentication request, the home storage system 10 collects content relating to the relevant device and transfers both to the online storage system 18; and if the content collected by the home storage system 10 matches key-content recorded as authentication information, the online storage system 18 transfers the recorded account information to the home storage system 10. The home storage system 10 can execute user authentication processing by using the account information transferred from the online storage system 18.