This invention relates to a positive photosensitive resin composition allowing development with an alkaline aqueous solution and excellent in resolution, photosensitivity and pattern form even if the film formed from the resin is thick. Furthermore, this invention relates to a photosensitive resin composition comprising (a) a polymer having one or more phenolic hydroxyl groups, (b) a compound having a phenolic hydroxyl group and containing only one group selected from a methylol group and alkoxymethyl group, and (c) a photo acid generator.