The thermosetting resin composition which is valuable for an undercoat of a printed wiring board, and does not leave an air bubble in a cured film, and makes the surface polishing easy and can form a smooth printed wiring board comprises (I) an adduct of epoxy resin with unsaturated aliphatic acid, (II) a (meth) arcylate, (III) a radical polymerization initiator, (IV) a crystallizable epoxy resin, and (V) a latent curing agent.