Provided is a cylinder block which includes a liner and a water jacket having a closed-deck structure in a simple configuration and which has a structure providing high rigidity and enabling easy formation at low cost. A cylinder block of the present invention includes a liner arranged on an inner circumference surface of a bored hole and a water jacket arranged on the outside of the liner in the radial direction. By a bending process of folding back an end portion of a cylinder-shaped member, a hollow portion capable of forming the water jacket is formed integrally in one end portion or both end portions of a liner portion forming the liner, and the cylinder-shaped member is enclosed with a cylinder block forming material by casting.