Cylinder bore wall heat insulation device, internal combustion engine and vehicle

A cylinder bore wall thermal insulator is provided to a middle-lower part of a groove-like coolant passage of a cylinder block included in an internal combustion engine that includes a plurality of cylinder bores, and insulates part of a cylinder bore wall, the cylinder bore wall thermal insulator including a rubber member that comes in contact with part of a cylinder bore-side wall surface of the middle-lower part of the groove-like coolant passage that covers one cylinder bore, or covers two or more cylinder bores, a metal base member on which the rubber member is secured, and an elastic member that is provided to the metal base member, and biases the metal base member so that the metal base member presses the rubber member against the cylinder bore-side wall surface of the middle-lower part of the groove-like coolant passage, one or more elastic members being provided to each bore-covering part of the metal base member. The cylinder bore wall thermal insulator can selectively insulate an area of the cylinder bore wall that requires thermal insulation, and is rarely displaced due to vibrations or the flow of the coolant.