A radio network controller (200) that serves to reduce the amount of processes for searching for a common ID in a paging procedure when performing a paging processing for simultaneously calling a mobile station (300). A search-not-required flag indicating whether or not a search for the common ID is required is added to a message (14' or 15') from a core network (400 or 500). The radio network controller (200) determines whether or not a search for the common ID is required based on the status of the flag and the type of the message (14' or 15') from the core network (400 or 500). A search for the common ID (21) is required if the flag is "OFF," whereas if the flag is "ON" and if the message (15') is paging 1, it is determined that an RRC connection has not been established for the mobile station (300) and thus a search for the common ID is not required in the radio network controller (200).