Directed to an insulating resin composition which comprises (A) a novolak epoxy resin having a biphenyl structure, (B) carboxylic acid-modified acrylonitrile butadiene rubber particles, (C) a triazine ring-containing cresol novolak phenolic resin, (D) a phenolic hydroxyl group-containing phosphorus compound, and (E) inorganic filler, an insulating film having a support using the same, a multilayer wiring board, and a process for producing a multilayer wiring board.