A coating composition capable of forming a curable coating layer having a sufficient dyeability on a resin substrate and improving adhesion after dyeing between the resin substrate and the curable coating layer, and a resin product having optical permeability applied with the curable coating layer by the composition are provided. The coating composition contains an ingredient (A): a hydrolyzate of an organosilane with the content of a bifunctional organosilane of from 50 to 100% by weight, an ingredient (B): colloid particles of metal oxide, and an ingredient (C): a solvent.