To improve heating performance without degrading fuel consumption.

A cooling system for a vehicle includes: a heating medium circulating means 2 for circulating a heating medium for cooling a vehicle driving energy generating means 1 in a heating medium circuit; electric component cooling means 3 and 4 for cooling electric components using the heating medium; radiators 5 and 6 for radiating heat of the heating medium to air; heat exchangers 7 and 8 for heating, by which heat exchange is performed between the heating medium and air flowing to the inside of a cabin; and valve means 21 and 22 which switches the flow of the heating medium according to the temperature of the heating medium to a plurality of modes. The plurality of modes includes a radiator bypass mode in which the heating medium flows while bypassing the radiators 5 and 6, and a radiator circulating mode in which the heating medium flows through the radiators 5 and 6. The valve means switches a flow to the radiator bypass mode, when the temperature of the heating medium is lower than a first predetermined value, and to the radiator circulating model, when the temperature of the heating medium reaches the first predetermined value.