A method and device for selecting a service domain in a system for setting a session for at least one or more services between at least two or more terminals, in which when receiving an INVITE message for setting a voice service related session from an originating terminal, it is decided whether to send the INVITE message to a server or to directly send the INVITE message to a terminating terminal according to user pre-registered information for a domain selection, and then the terminating terminal having received the INVITE message sends to a network a response message including domain selecting information for directly selecting a domain with respect to the voice service related session according to a user's selection.