A radio communication system comprising: a radio base station that is configured to manage a cell, mobile terminals that are configured to connect to the cell and measure radio channel quality of the cell and radio channel quality of specific neighbor cells of neighbor cells that are in the vicinity of the cell, and a self-optimizing system that is configured to set a radio parameter on said radio base station, wherein said self-optimizing system comprises: an update value calculation section configured to calculate an update value of a determining factor of the radio parameter based on communication traffic statistics information of the cell and the neighbor cells and on radio channel quality information that indicates radio channel quality measured by said mobile terminals; a reliability evaluation section configured to evaluate the reliability of the update value of the factor calculated by said update value calculation section; an update determination section configured to determine whether or not to apply the update value of the factor to said radio base station, based on the evaluation result by said reliability evaluation section; and a radio parameter updating section configured to set the radio parameter determined by the update value of the factor in said radio base station when a determination is made that the update value of the factor is to be applied to said radio base station; wherein said reliability evaluation section is configured to calculate the reliability of the update value of the factor as an output of an evaluation function that inputs the number of mobile terminals connected to the cell or the number of reports of the radio channel quality information received from the mobile terminals; and wherein the update determination section is configured to determine to apply the update value of the factor to said radio base station when the evaluation result by said reliability evaluation section is larger than a predetermined threshold. a radio base station that is configured to manage a cell, mobile terminals that are configured to connect to the cell and measure radio channel quality of the cell and radio channel quality of specific neighbor cells of neighbor cells that are in the vicinity of the cell, and a self-optimizing system that is configured to set a radio parameter on said radio base station, wherein said self-optimizing system comprises: an update value calculation section configured to calculate an update value of a determining factor of the radio parameter based on communication traffic statistics information of the cell and the neighbor cells and on radio channel quality information that indicates radio channel quality measured by said mobile terminals; a reliability evaluation section configured to evaluate the reliability of the update value of the factor calculated by said update value calculation section; an update determination section configured to determine whether or not to apply the update value of the factor to said radio base station, based on the evaluation result by said reliability evaluation section; and a radio parameter updating section configured to set the radio parameter determined by the update value of the factor in said radio base station when a determination is made that the update value of the factor is to be applied to said radio base station; an update value calculation section configured to calculate an update value of a determining factor of the radio parameter based on communication traffic statistics information of the cell and the neighbor cells and on radio channel quality information that indicates radio channel quality measured by said mobile terminals; a reliability evaluation section configured to evaluate the reliability of the update value of the factor calculated by said update value calculation section; an update determination section configured to determine whether or not to apply the update value of the factor to said radio base station, based on the evaluation result by said reliability evaluation section; and a radio parameter updating section configured to set the radio parameter determined by the update value of the factor in said radio base station when a determination is made that the update value of the factor is to be applied to said radio base station; wherein said reliability evaluation section is configured to calculate the reliability of the update value of the factor as an output of an evaluation function that inputs the number of mobile terminals connected to the cell or the number of reports of the radio channel quality information received from the mobile terminals; and wherein the update determination section is configured to determine to apply the update value of the factor to said radio base station when the evaluation result by said reliability evaluation section is larger than a predetermined threshold.