Abstract: The present invention provides a photosensitive insulating resin composition which can be cured at low temperatures without inhibiting functions of an organic semiconductor device or the like, by the use of which a cured product excellent in various properties such as resolution, electrical insulation, thermal shock resistance and chemical resistance can be obtained and which is suitably used for a surface protective film or a layer insulating film of a semiconductor device. The photosensitive insulating resin composition of the present invention comprises a copolymer (A), which is obtained by copolymerizing monomer components containing a vinyl monomer having an epoxy group and a vinyl monomer having an oxetanyl group, and a photosensitive acid generator (B). The copolymer (A) is preferably obtained by copolymerizing monomer components containing a vinyl monomer having an epoxy group, a vinyl monomer having an oxetanyl group and another vinyl monomer.