According to one embodiment, an account aggregation system includes an information processing apparatus and an account aggregation server. The information processing apparatus includes a database, an automatic sign-on process module and an encryption key processing module. The automatic sign-on process module is configured to provide authentication data the service providing servers have requested for, by using the authentication data stored in the database. The encryption key processing module is configured to register, for the account aggregation server, an encryption key for encrypting authentication data to be stored in the database or for decrypting the authentication data stored in the database, to acquire the encryption key from the account aggregation server when a process is performed by using the encryption key, and to erase the encryption key after the process is performed. The account aggregation server includes an encryption key management module which is configured to manage the encryption key.