The present invention relates to a resin composition which includes a copolymer consisting of a first monomer containing a monomer unit having at least one carboxyl group and a second monomer copolymerizable with the first monomer, and also includes an ultraviolet absorber. The resin composition used is a resin composition for which, when ∈1 represents an absorbance coefficient per unit weight of a resin film 2 in a solution prepared by dissolving, in a solvent, the resin film 2 formed by application of the resin composition as a liquid, ∈1 at a light wavelength at which the resin film 2 is to be irradiated is at least 0.01 (L/(g·cm)).