To provide a thermocurable resin composition from which a cured product, that satisfies thermal curability, PCT resistance, solvent resistance and peel strength simultaneously, can be obtained.

A thermocurable resin composition, which is used as a resist layer of a printed circuit board, contains carboxyl group-containing polyimide and a compound containing an oxirane ring. The carboxyl group-containing polyimide has such a structure that a chain of an imide prepolymer containing a terminal acid anhydride, which prepolymer is obtained by reacting an acid anhydride group in a tetracarboxylic acid dianhydride with an isocyanate group in a diisocyanate compound, is extended while interposing a polyol compound therebetween.