To improve cleaning effects by a method, wherein each stage is brought into a clean N2 gas atmosphere, wafer are treated by a chemical solution, the wafers are cleaned with ultrapure water, they are dried up, by blowing clean N2 gas on IPA paper from the upper surface of the wafers.

The chamber of a bath is brought into a clean N2 gas atmosphere, and a plurality of wafers 3 are superposed at regular intervals at the bottom stage. The plural wafers 3 are rotated simultaneously, a chemical fluid is sprayed on the surface while the wafers 3 rotate, and the wafers are treated by the chemical fluid. Then, the wafers 3 are moved to the middle stage, and they are cleaned by ultrapure water in the same manner as in the bottom stage. After the cleaning is finished in this manner, the wafers are rotated by 90 degrees simultaneously, hot clean N2 gas of 120°C is blown against both the surfaces of the wafers 3. Then, the wafers are dried up by blowing clean N2 gas on the IPA paper from the upper surface of the wafers 3.