1. An apparatus for optimizing a neighbor list for handover in a mobile communication system, comprising: a data collecting unit configured to collect wireless quality measurement data and call fault data of a mobile communication terminal, wherein the call fault data indicates information regarding a call fault event generated due to absence of sub-cell information in the neighbor list when the mobile communication terminal carries out a handover; a data analyzing unit configured to analyze the wireless quality measurement data and the call fault data and calculate a first frequency of a sub-cell being included in an active set for each handover-possible target sub-cell and a second frequency of call fault event occurrence, wherein the first frequency is calculated based on the sub-cell and target sub-cell being included simultaneously in the active set for handover; and a neighbor list optimizing unit configured to i) set an order of priority of handover-possible target sub-cells for the sub-cell based on the first and second frequencies and ii) generate a neighbor list corresponding to the order of priority in conjunction with a processor, wherein the neighbor list optimizing unit is adapted to i) configure a weighting factor based on the difference in the number of samples between the wireless quality measurement data and the call fault data and ii) determine the order of priority based on the multiplication of the weighting factor and a call fault event frequency.