According to one embodiment, an interface apparatus includes a connector which establishes connection with a plurality of Session Initiation Protocol (SIP) terminals which each include communication functions defined by SIP and with an SIP network to one port, a first processor which executes exchange processing for the plurality of SIP terminals, a second processor which executes exchange processing for the SIP network, and a sorting unit which sorts a control signal into the first processor or the second processor based on transmission destination identification information or transmission origin identification information in the control signal regarding exchange received by the connector.