Abstract: A coated cemented carbide endmill comprises a tungsten carbide based cemented carbide substrate comprising 5-20% Co as a binder phase forming component, optionally 0.1-2% of Cr and/or V as a binder phase forming component, optionally 0.1-5% of one or more of (Ti, Ta, Nb, Zr) C·N as a dispersed phase forming component, and the balance being WC as the dispersed phase forming component and inevitable impurities. The WC has a fine grained structure having an average grain size of 0.1-1.5 &mgr;m, the cemented carbide substrate has a reaction-created surface layer formed on the surface portion thereof which is formed by heating at high temperature and in which ComWnC is distributed over a thickness of 0.1-2 &mgr;m thereof, and further the substrate has coated layers composed of a Ti compound layer. Optionally, an Al2O3 layer is formed thereon with an average layer thickness of 0.5-4.