The invention relates to a heat radiating device of flat water tank for computers and electrical apparatus, comprising the flat water tank, an
impeller window component, a soft
pipe, a
water cooling head and a power supply module, wherein the
impeller window component has three functions for observing the dynamic state of the
impeller window component, observing the
water level of cooling liquid and being used as a water
injection port of the flat water tank; the flat water tank has two functions of being used as a tank shell and radiating; and the tank body is formed by bonding, sealing and
welding a flat plate and a corrugated plate, wherein antifreezing cooling liquid can be contained in the convex space of the corrugated plate; after the convex space, the soft
pipe, the
water cooling head and the impeller window component are closed and assembled, a closed
water circulation device is formed; and automatic circulation is realized by the characters of expansion and raise by heat and shrinkage and reduction by cold, without using a water pump as power. The heat of a computer CPU and the power supply module is brought to the flat water tank by
water circulation; and the flat water tank is used for naturally cooling air and radiating the heat, thereby achieving the purpose for quietly cooling in an energy saving mode. The flat water tank is combined with the power supply module for saving a power fan of a desktop computer. The flat water tank can be also used for
electrical equipment needing cooling and not needing
fan noise and radiators used as refrigerating equipment, such as water machines, refrigerators and the like which have certain requirements on appearance.