Abstract: A surface coated tungsten carbide-base sintered hard alloy material for inserts of cutting tools having excellent wear resistance and toughness comprising(1) a substrate having an internal portion consisting essentially of 5-30 percent by weight of one composite metal carbo-nitride, as a compound forming a hard dispersion phase, selected from the group consisting of (Ti, W)CN, (Ti, Nb, W)CN, (Ti, Ta, W)CN, and (Ti, Nb, Ta, W)CN; 4-10 percent Co as a component forming a binder phase, and the balance of WC as a component forming the hard disperse phase and inevitable impurities; the substrate having a surface portion formed with a Co-enriched layer being substantially free of the composite metal carbo-nitride; and(2) a hard surface layer coated over the surface of the substrate, comprising an innermost layer consisting essentially of TiC, the innermost layer containing one of a W component and W and Co components diffused from the substrate; a diffusion preventing layer formed by one of a single layer of one co