Abstract: A cylinder structure of a diesel engine in which diesel fuel is ignited by a self-ignition manner includes a cylinder including a cylinder body in which a combustion chamber is formed and a cylinder head covering an upper portion of the cylinder body, at least one intake valve included in an intake port formed in the cylinder head, at least one exhaust valve included in an exhaust port formed in the cylinder head, and a diesel injector mounted at the center of the cylinder head and injecting diesel fuel. A lower surface of the cylinder head may be formed in a pent roof shape.