To obtain a water-based coating composition containing an emulsified polymer of black japan at a specific ration to the vehicle, giving jet-black coating layer excellent in deep and clear tones and useful in coating household electric appliances which are required to have high-quality appearance and in household articles.

This coating composition contains (A) an emulsified polymer of black japan and (B) a vehicle (other than the component A) at a weight ration of (A) (10-70)/(B) 100 in solid basis. The component A is preferably prepared by subjecting a japan component containing urushiol such as purified japan or black japan to oxidative polymerization in an aqueous solution and suspending or emulsifying the polymer in the vehicle comprising a water-based film-forming polymer mixed with a curing agent. The water-based film-forming polymer is a polymer which can be appropriately used as a component B. In an embodiment, an aqueous acrylic polymer, an aqueous polyester resin and the like can be used. The curing agent is, for example, a melamine resin, blocked polyisocyanate and the like.