A first mobile terminal group has a first measurement information transmitting means which measures radio quality of a second cell, and transmits measurement information to a first base station, a second mobile terminal group has a second measurement information transmitting means which measures radio quality of a first cell, and transmits measurement information to a second base station, and a neighbor cell list optimizing system has: a measurement information collecting means which collects the measurement information of the first and second cells; a reliability evaluating means which performs processing of evaluating reliability of the measurement information of the second cell; a priority calculating means which, when the reliability is a predetermined threshold or less, calculates a priority for registering the second cell in the neighbor cell list of the first cell based on the measurement information of the first cell; and a neighbor cell list updating means which performs control of determining a neighbor cell to be registered based on the priority, and updating the neighbor cell list.