The present invention provides a diamond sintered compact tool. Which is excellent in economy as well as cutting edge strength. A diamond sintered compact cutting tool comprising a diamond sintered compact sintered at an ultra-high pressure and high temperature and a WC—Co cemented carbide substrate directly bonded to the diamond sintered compact during a step of sintering and brazed to a tool base through the WC—Co cemented carbide substrate, in which a ratio of the thickness of the WC—Co cemented carbide substrate to the thickness of the diamond sintered compact layer satisfies the relation of: 0.8≦WC—Co cemented carbide substrate/diamond sintered compact layer≦3.0 and the diamond sintered compact layer has a thickness of 0.05 mm to 0.5 mm, preferably 0.05 mm to 0.45 mm, more preferably 0.12 mm to 0.36 mm.