A liquid cooling system includes a heat-radiating sheet having a pair of heat-conductive metal plates that are superimposed on each other, and having a circulating flow passage between the pair of heat-conductive metal plates; a plurality of heat-receiving areas partitioned on the heat-radiating sheet; a plurality of heat-generating elements installed on each of the heat-receiving areas via a heat spreader made of a heat-conductive material; an inlet hole and an outlet hole opened to the surface of the heat-radiating sheet and located at both ends of the circulating flow passage; a pump having a discharge port and a suction port that communicate with the inlet hole and the outlet hole, and installed on the heat-radiating sheet; and a radiator continuous with the circulating flow passage of the heat-radiating sheet.