To prevent a substrate from being immersion-processed until the concentration of a chemical contained in a treating solution becomes a prescribed value when the treating solution is supplied or replaced to a treatment tank.

A circulating route is formed so as to circulate a treatment solution overflowing a treatment tank CB to the tank CB again by means of circulating pump P through a temperature regulator 15, a concentration meter 10b, and a filter F after the overflowing solution is received by means of a circulating tank SB. In order to measure the concentration of the treating solution, concentration meters 10a and 10b are respectively installed to the tank SB and the circulating route. At the time of exchanging the treating solution, various kinds of chemicals are supplied to the tank CB by opening V1, V2, and V3. After the circulation of the treating solution is repeated for a prescribed period of time by means of the pump P thereafter, the concentration of each chemical is measured with the concentration meters 10a and 10b. When the concentration of one chemical is abnormal, substrate treatment is not started, but the treating solution is again replaced or a required chemical is additionally supplied.