Disclosed are an SIP-based user mobility service providing apparatus and method using user position information obtained by a sensing apparatus. When a user enters a specific region, a gateway including a sensing management module carries out SIP registration for several terminals existing in the specific region in place of user agents of the terminals. The sensing management module transmits an SIP registration message to an SIP proxy server and notifies the terminals of the completion of SIP registration. Then, the user receives a call using the same kind of a terminal as a specific terminal previously set on the basis of a user's preferences among the terminals in the specific region.