A cooling apparatus includes a cooling passage provided in an internal combustion engine, a water pump, a radiator, a first passage through which the water pump and the cooling passage are connected to each other, a second passage through which the cooling passage and the radiator are connected to each other, a third passage through which the radiator and the water pump are connected to each other, and an oil cooler passage provided with an oil cooler. An in-line type thermostat is provided at any position in a portion of a cooling water circuit which leads from a first end portion to a second end portion via the second passage, the radiator, and the third passage.