COMMUNICATION APPARATUS

PROBLEM TO BE SOLVED: To provide technique capable of improving convenience in the notification of incoming calls and calls in multiple accounts.SOLUTION: A communication apparatus to be connected to an IP telephone system by using the Internet includes user accounts, authentications, a group account, and a group account authentication as a sign-in method for an IP telephone, so that the multiple user accounts and their respective authentications are allocated to the group account. Besides, the communication apparatus to be connected to the IP telephone system by using the Internet includes the user accounts and the authentications, authenticates the account different from the account during sign-in, thereby to enable the simultaneous sign-in of the multiple accounts as the sign-in method for the IP telephone.