Abstract: A water supply apparatus and a method thereof have a high capability of peeling-off and removing unnecessary objects such as a resist film, and parameters for setting efficient water supply conditions. The water supply apparatus and the method are designed to supply water for cleaning, peeling-off, or treating a target article. On a surface of the target article to be processed, a nozzle device is provided for spraying a mixture of water vapor and water mist. At least the following parameters are respectively set as water supply conditions to proper values so as to supply water to the target article, and these parameters include (1) a weight ratio of water vapor to water mist on the surface to be processed, (2) a temperature of the surface to be processed, and (3) a distance between a (water) blowing port of the nozzle device and the surface to be processed.