PURPOSE: To carry out the effective cooling by the engine cooling water even if a turbocharger is at a position over an engine by installing each communication water conduit in a cooling water passage for the turbocharger, radiator outlet, and a cooling water passage in the engine.

CONSTITUTION: During the operation of an engine 5, a water pump 8 is driven by the engine 5, and cooling water is sent into a cooling water passage in the engine 5, and after absorbing the heat of each part of the engine 5, water reaches a radiator 10 through a thermostat 9 and liberates the heat absorbed from each part of the engine 5 and is sent into the inside-engine cooling water passage by the pump 8 again. Further, a portion of the cooling water reaches the cooling water passage 4 of a turbocharger 1 through a water conduit 11 from the outlet of the radiator 10, and after absorbing the heat of a bearing part 3, water is returned into the cooling water passage in the engine 5 through a water conduit 12, and then reaches the radiator 10 through the thermostat 9. When the engine 5 stops, the cooling water in the radiator 10 having a low temperature flows into the cooling water passage 4 of the turbocharger 1 through the water conduit 11 by the inertial force, and cools the bearing part.