Provided is a resin containing a carboxyl group, which is suitable as a component of a photosensitive resin composition, can impart excellent developability with an alkaline aqueous solution to a photosensitive resin composition even though the resin has a fluorene skeleton, and can also impart high electric insulation properties and plating resistance to a cured product of a photosensitive resin composition. The resin containing a carboxyl group is a reaction product of an intermediate with an acid dianhydride and an acid monohydride, wherein the intermediate is a reaction product of an epoxy compound having a bisphenol fluorene skeleton represented by formula (1) with a carboxylic acid containing an unsaturated group. The degree of polydispersion of the resin containing a carboxyl group is in the range from 1.2 to 2.8.