A liquid cooling system is disclosed for use in an electronic apparatus. The system is constructed to be of a reduced size and thickness, thus allowing it to be used for cooling heat-generating devices such as semiconductor elements, while maintaining corrosion resistance. The system includes a pump, a heat-receiving jacket, and flow passages through which the cooling liquid is circulated. An ion exchange bag having a water-permeable bag is disposed within the liquid cooling system. The water-permeable bag further contains an ion exchange resin therein.