A mobile network system includes a guidance message control server, a call control server and access gateways. The call control server receives a call request notification from a first access gateway, determines whether a second access gateway is connected to a second mobile terminal, transmits a message transmission instruction to the guidance message control server and transmits a response message including a same group specifying information. The guidance message control server receives the message transmission instruction from the call control server, acquires guidance message data specified by a message specifying information and multicast transmits the guidance message data to a multicast group specified by the group specifying information. The first access gateway receives a call connection request from the first mobile terminal and transmits the call request notification to the call control server, performs multicast group participation processing for participating in the multicast group and transmits the guidance message data.