An organic composite coated steel sheet having a high cosmetic corrosion resistance and excellent image clarity which is desired on, for example, the outside of an outer plate forming an automobile body. The steel sheet has a chromate layer formed on the surface of a zinc or a zinc alloy plate steel sheet, and containing a specific weight of chromium, and an organic resin film formed on the chromate layer from a mixture in specific proportions of a blocked urethane-modified epoxy resin and a rust-preventing additive, and having a thickness of 0.2 to 2 microns. The resin is a mixture in specific proportions of a modified epoxy resin (A) which consists of an epoxy resin and a polyfunctional amine, and may further contain a monoisocyanate, or phosphoric acid, and a blocked urethane (B) which consists of a high molecular weight polyol having a molecular weight of 400 or more, a polyisocyanate and a blocking agent. A process for manufacturing the strip is also disclosed.