The disclosure herein provides a heat management system for a vehicle, comprising: a first heat circuit in which first heat medium flows; a second heat circuit in which second heat medium flows; and a main heat exchanger configured to transfer heat from the second heat medium to the first heat medium. The first heat circuit comprises: a compressor; a cabin heater; a first air heat exchanger; an evaporator; a first bypass channel configured to allow the first heat medium to bypass the main heat exchanger; and a first switching valve by which one of the main heat exchanger and the evaporator is selected as a flow destination of the first heat medium flowing out from the first air heat exchanger. A single heat circuit (the first heat circuit) can achieve both heating and cooling of the air in the cabin.