A closed container composed of a lid body and a lower container are provided in a cover body, and a supply pipe for nitrogen gas is connected to the cover body. A light source unit including UV lamps in the lid body is provided to face a mounting table in the closed container, and a gas supply path for HMDS gas is provided on the outer side from the light source unit. The inside of the cover body is first brought to a nitrogen atmosphere, a wafer is irradiated with ultraviolet rays with the lid body of the closed container opened to perform cleaning. Subsequently, the lid body is closed and the HMDS gas is introduced into the closed container to perform hydrophobic processing for the wafer. This removes deposits such as organic substances adhering to the wafer W through the irradiation with the ultraviolet rays, thereby improving coating properties of a resist solution.