An apparatus and a method for allocating a Device-to-Device (D2D) IDentity (ID) of a user terminal in an ad-hoc network are provided. The method includes determining that a first D2D ID allocated to the user terminal is duplicated with a second D2D ID allocated to at least one other terminal located within a predefined range from the user terminal, determining whether the user terminal is in communication, when the first D2D ID is duplicated with the second D2D ID, and changing the first D2D ID into a third D2D ID with reference to a D2D ID pool so that the first D2D ID is not duplicated with the second D2D ID, when the user terminal is not in communication.