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.