An electronic apparatus, such as, personal computers of so-called a desktop type and a notebook type, as well as, a server, etc., having a cooling system being high in cooling efficiency, wherein a CPU 200 in need of cooling is installed within a hosing 100, and the liquid cooling system for cooling the CPU, comprises: a heat-receiving (cooling) jacket 50; a radiator 60; and a circulation pump 70, wherein the heat-receiving (cooling) jacket 50, for transmitting heat generated from a heat-generation element, i.e., the CPU, into a liquid coolant flowing with in an inside thereof, has a heat diffusion plate 90 attached on the lower surface thereof. This heat diffusion plate encloses an operating fluid 94, such as water, within a space, which is hermetically sealed and formed within an inside thereof, and also has heater elements 95, being provided in contact with a portion the operating fluid. To those heater elements 95 are supplied a pulse-like electric power. With this, a portion of the operating fluid repeats forming/extinguishing, to give vibration to the operating fluid, thereby diffusing the heat over the entire of the diffusion plate, as a whole, thereafter the heat is transmitted to the heat-receiving (cooling) jacket. Or, alternatively, it may be connected with a heat radiation fin 300.