Ultraviolet rays are radiated over a lubricant film formed on the surface of a recording medium such as a hard disk. The recording medium is then subjected to exposure to a bases. The radiation of the ultraviolet rays allows the lubricant film to uniformly spread over the surface of the recording medium. The repellency can be enhanced over the surface of the recording medium. The friction can be reduced on the recording medium. Moreover, when the recording medium is exposed to the base, organic acid existing on the surface of the recording medium and/or in the lubricant film can be transformed into salt. The organic acid can be washed off or removed from the surface of the recording medium and/or out of the lubricant film in this manner. Less organic acid greatly contributes to prevention of generation of corrosion mounds on the recording medium over a longer period.