In a wireless cell, the potential deterioration in quality is efficiently detected when the indication of abnormalities is weak. Provided are a step of calculating one or more radio qualities for each coverage area of a wireless cell; a step of measuring one or more network statistical qualities for each coverage area of the wireless cell; a step of making a pair of each network statistical quality and one or more radio qualities for each coverage area of each wireless cell; and a step of calculating, based on the pairs of each network statistical quality and one or more radio qualities for the coverage areas of the wireless cells, the correlation between each network statistical quality and one or more radio qualities.