To increase a combustion performance and a fuel consumption performance with a simple structure by rapidly increasing the temperature of a cylinder block 12 when a machine is cooled, and rapidly reduce a friction by rapidly increasing the temperature of engine oil.

The cylinder block 11 and a cylinder head 12 are installed, parallel with each other, on the downstream side of a water pump. A radiator 13 and an oil cooler (auxiliary heat exchanger) 14 are installed, parallel with each other, on the upstream side of the water pump. A cooling water regulating valve 30 is installed to cut out a block side outlet passage 21 for cooling water flowing out of the cylinder block 11 and cut out an auxiliary inlet passage 24 for cooling water flowing into an oil cooler 14.