Disclosed is a method for determining handover of a mobile station by a mobile station in a mobile communication system. The method includes measuring a downlink reference signal intensity of a serving base station; determining to perform scanning for measurement of reference signal intensities of the serving base station and neighbor base stations, when the measured downlink reference signal intensity of the serving base station is less than a reference value, negotiating with the serving base station for a scanning period and the number of scanning repetitions, measuring the reference signal intensities of the serving base station and the neighbor base stations, and resetting the reference value when a reference signal intensity of the serving base station is greater than or equal to reference signal intensities of neighbor base stations.