Cylinder head structure of a direct-injection diesel engine and a direct injection diesel engine

A cam holder 31, constructed separately from a cylinder head 10, for supporting an intake and exhaust camshaft 26 is mounted on a middle deck of the cylinder head 10. At end pivots 27 of each swing arm 25 located at both the right and left ends when viewed from the front of the engine, mechanical lash adjuster mechanisms are provided, respectively. The height of a peripheral wall at both the right and left sides adjacent to the end pivots 27 is located lower than a mating surface between a cam journal 33 and a cam cal 34 of the cam holder 31.