A liquid cooling system, comprises: heat-receiving jacket 7, thermally connected with a heat-generation element, a pump attached onto a radiator 1a, and a tank portion 2 on the radiator 1a, wherein a coolant liquid is circulated between the heat-receiving jacket 7 and the radiator 1a by means of the pump 8, thereby obtaining the liquid cooling system for an electronic apparatus, being suitable for small-sizing and a thin-type, while maintaining high reliability thereof.