PURPOSE: To provide the diamond coated hard material having excellent adhesive strength, high toughness and high degree of shape freedom and the process for production of this material.

CONSTITUTION: This diamond coated hard material is constituted by coating the surface of a base material which is a hard material consisting of a hard phase component and a bond phase component with diamond. The material contains a B-1 type solid soln. having a crystal structure of a face-centered cubic crystal system constituted of at least ≥1 kinds among the carbide, nitride, carbonnitride, oxide, boride, borocarbide, boronitride and borocarbonitride of group 4a, 5a, 6a metals of periodic table and the solid solns. thereof as the hard phase component and satisfies an one or over of the requirements that the lattice constant of the B-1 type solid soln. on the front surface of the base material is smaller than the internal lattice constant or the ratio of the W atoms in the B-1 type solid soln. on the front surface is smaller than in the inside or the lattice constant of the B-1 type solid soln. is ≤4.364. A WC-based cemented carbide is exemplified as the more particularly preferable hard material.