Abstract: A cooling system for a vehicle includes a flow channel circulating a liquid medium cooling a drive device of the vehicle, a plurality of temperature sensors provided at different positions on the flow channel, a heating element provided on the flow channel and cooled by the liquid medium, and a control device controlling heat generation from the heating element. The control device changes a heat generating state of the heating element, and estimates a flow rate of the liquid medium flowing through the flow channel based on a time lag taken for detecting a temperature change caused by changing the heat generating state by the plurality of temperature sensors. Preferably, the drive device includes a motor, and a power control unit for driving the motor, and the heating element is a power control element in the power control unit.