To provide: an unsaturated group-containing alkali developable resin which has excellent developability and provides a cured product having excellent heat resistance and dielectric characteristics; a photocurable alkali developable resin composition which contains this unsaturated group-containing alkali developable resin; a cured product of this photocurable alkali developable resin composition; a resin material for solder resists; and a resist member. An unsaturated group-containing alkali developable resin which has a molecular structure obtained by reacting, as essential starting materials, (A) a polyepoxy compound, (B) an unsaturated monocarboxylic acid, (C) an unsaturated monocarboxylic acid anhydride and (D) a dicarboxylic acid anhydride, and which has an acid value within the range of 50-80 mgKOH/g and a hydroxyl number of 19 mgKOH/g or less.