A heat exchanging system exchanging heat between refrigerant and a battery includes: a compressor circulating refrigerant; a heat exchanger exchanging heat between the refrigerant and outside air; an expansion valve decompressing the refrigerant; a heat exchanger exchanging heat between the refrigerant and air-conditioning air; a heat exchanging portion connected in parallel with the heat exchanger and exchanging heat between the refrigerant and the battery; a bypass passage providing fluid communication between a path of the refrigerant between the compressor and the heat exchanger and a path of the refrigerant between the expansion valve and the heat exchanger; an expansion valve provided in the bypass passage and decompressing the refrigerant flowing through the bypass passage; and a selector valve allowing or interrupting flow of the refrigerant via the bypass passage.