The state of a photosensitive material processing solution is easily determined from values of multi-dimensional analysis by utilizing Mahalanobis distance. The Mahalanobis distance is calculated, and a determination is made as to whether or not the Mahalanobis distance is greater than or equal to a threshold value. If the Mahalanobis distance is less than the threshold value, the processing solution is determined to be normal, the Mahalanobis distance is displayed on a display unit, and a determination is made as to whether or not the number of sets m of normal values has become greater than or equal to a predetermined value m.sub.0. If m.gtoreq.m.sub.0, data of the characteristic values in the oldest set in a time series is deleted, and a set of data of newly detected characteristic values is added to calculate the Mahalanobis distance and update a database. If the Mahalanobis distance is greater than or equal to the predetermined value, a developing solution is determined to have become abnormal, the degree of abnormality is displayed, factors which caused the abnormality are determined, a corrective measure is determined on the basis of a combination pattern of factors, and the measure is displayed.