PURPOSE: To obtain a hard and high strength composite material containing diamond even under low pressure by simultaneously using both plasma jet method and plasma spraying method.

CONSTITUTION: The inside of a vacuum tank 1 provided with a plasma jet gun 2, a plasma spray gun 3, a substrate 4, etc., is regulated to the prescribed vacuum state, and gaseous raw materials are introduced via supply pipes 2a, 2b, 2c, 3a, 3b into respective guns 2, 3 and also a ceramics as raw material is introduced via a supply pipe 3c into the gun 3. Subsequently, the gaseous raw materials, such as CH4, are sprayed from the gun 2 on the substrate 4 to perform the synthesis of diamond, and simultaneously, the ceramics as raw material, such as titanium carbide, is sprayed from the gun 3, by which a mixed film of diamond and ceramics is formed. By this method, the hard and high strength composite material containing diamond can be obtained.