ENGINE COOLING DEVICE

The cooling device 1 includes the engine 50 having a cylinder block 51 provided with a partial W/J 511 a circulating a coolant in a periphery of a cylinder 51a. In the cooling device 1, an outer wall portion W2 of a wall portion forming the partial W/J is made of a material having a heat conductivity lower than a material of an inner wall portion of the wall portion, the inner wall portion W1 facing the outer wall portion W2 and being located in the cylinder 51a side.