Abstract: Disclosed is a coating resin composition obtained by graft-polymerizing an unsaturated carboxylic acid to a chlorinated polyolefin in a solvent, esterifying all unsaturated carboxylic acid present in the reaction system, and mixing the obtained composition with a urethane prepolymer so that the weight ratio of the solids of the composition to the solids of the urethane prepolymer is in the range of from 90/10 to 10/90. This composition has a greatly improved gasoline resistance, smell generation is controlled and the storage stability at low temperature is high. The composition is effective as a general-purpose primer showing a high adhesion to inorganic materials, polar resins, non-polar resins, metals, and other materials.