Cylinder block of plural cylinder engine

Object In a cylinder block of plural cylinder engine, having: a cylinder main body in which plural cylinder bores (22A,22B) are provided in parallel in an axial direction of a crankshaft; and a crankcase having plural journal walls (23B), integrally provided with the cylinder main body, in which a communication hole (26) extending in parallel to the axial line of the crankshaft is provided in the cylinder main body and the crankcase while at least a part of which is opened in the inner peripheral surface of the cylinder bore (22A,22B), to downsize the cylinder block and increase freedom of positional setting of the communication hole, further to reduce ventilation resistance of air flow through the communication hole (26). Means of Solution A cut-processed member (30A) expanded further outward from a piston slide surface (19) is formed along a radial direction of cylinder bores (22A and 22B), in inner surfaces of the cylinder bores (22A and 22B) in at least portions closer to a piston at an open edge of a communication hole(26).