A technique for obtaining good film quality in forming a silicon-oxide-containing insulating film as a coating film on a substrate. A coating liquid containing polysilazane is applied to a wafer, a solvent in the coating liquid is volatilized, and then the coating film is irradiated with ultraviolet rays under a nitrogen atmosphere before performing a curing process. Thus, dangling bonds are likely to be formed at hydrolyzed portions in polysilazane. Since dangling bonds are formed in advance at portions in silicon to be hydrolyzed, productivity of hydroxyl groups is enhanced. That is, since an energy required for hydrolysis is reduced, the number of the portions remaining without being hydrolyzed is reduced even when the curing process is performed at a low temperature. Therefore, dehydration synthesis occurs efficiently, which increases a crosslinking rate and makes it possible to form a dense (good film quality) insulating film.