A method for allocating a resource by a Mobile Station (MS) in a mobile communication system includes performing a measurement operation and a measurement report operation; and being allocated a resource from a small cell Base Station (BS) or a macro BS based on a neighbor small cell BS change probability and a neighbor small cell BS list, wherein the neighbor small cell BS list includes information on neighbor small cell BSs, and the neighbor small cell BSs are neighbor small cell BSs of which received signal strengths for reference signals measured by the MS are equal to or greater than a threshold received signal strength, and wherein the neighbor small cell BS change probability is determined using a neighbor small cell BS list which is generated at a current timing point and a neighbor small cell BS list which is generated at a previous timing point.