PURPOSE: To provide a diamond polycrystal thin film-covered cemented carbide tool having high durability, and a method for manufacturing it.

CONSTITUTION: In a method for covering the surface of a WC cemented carbide tool having a Co content less than 6wt.% with a diamond polycrystal thin film, the Co component within the range of 3-50μm from the surface is eluted with HCl or N2NO3 aqueous solution to form a Co removed layer, and a Co oxidized layer is formed by anode oxidation in HCl aqueous solution. An electrolytic reaction is performed in NaOH aqueous solution with the tool as a negative electrode to peel and remove the Co removed layer and the Co oxidized layer, and a coat of diamond polycrystal thin film 7-30μm in thickness is applied by plasma method.