To provide a method for controlling a detergent solution in order to keep it in high detergency, good dryability and nonflammability.

The method comprises detecting the level of a dirty component contaminating into a nonflammable detergent or rinse by measuring changes in its property values including electric conductivity, light absorption and refractive index during a cleaning process, wherein the detergent or rinse contains (a) a non-chloric fluoride compound having a vapor pressure of 1.33×103 Pa at 20°C or more and (b) one or more compound having a vapor pressure of less than 1.33×103 Pa at 20°C and selected from the group consisting of ether bond- and/or ester bond-having organic compounds.