To die-cast mold a cylinder of a water cooling type mono-block engine, and reduce costs by integratedly form a cylinder head and a cylinder block part with each other, forming an upper end of the cylinder head part in an opening structure, and attaching a cover member.

A cylinder 2 manufactured by die-cast mold of aluminum is constituted by integrating a cylinder head part 3 and a cylinder block part 4 with each other, and a fuel injection valve inserting hole 5, each water jackets 6, 7 of a head side and a liner side, an exhaust port 8, and an intake port 9 are formed. The lower water jacket 7 is formed by using an annular hollow insert member 13 composed of an aluminum made thin plate as a core, and the exhaust port 8 and the intake port 9 are formed by a mold which is inserting set from a horizontal direction. The cylinder 2 is formed in an upper opening structure, and its opening part is closed by fastening an aluminum made cover member 18.