The present invention provides a resin composition for resist to be efficiently formed into a cured product with high properties of crack resistance, bulge resistance, protrusion resistance, and the like for filling a through-hole, a via hole, or the like with the cured product. The resin composition for masks in accordance with the present invention contains a first resin and a second resin. The first resin is prepared by an addition reaction of polybasic acid anhydride with an adduct of an ethylenically unsaturated compound having a carboxyl group and bifunctional epoxy resin. The second resin having; a group obtained by an addition reaction of an epoxy group with monocarboxylic acid; and a group obtained by addition reaction of an epoxy group with polybasic acid.