The Plate Cooler is the most simple structure heat exchanger, it consists of the thin plate with attached rubber gasket and it enables heat exchanger in a short time by using two fluid let flows between narrow gaps because the corrugation of the thin plate easily forms turbulent flow in the very low Reynolds number, the heat transfer coefficient of two kinds of liquid is generally 2~4 times larger than the heat exchanger of tubular type and heat exchange is efficient due to counter flow. Furthermore, plate cooler is very ideal heat exchanger even in the temperature higher than 1℃ contrary to tubular type whose temperature approach is over 4℃。 In addition, it is one of the most important machines in the ship because it makes Main Engine, Generator Engine and other auxiliary machine exchange heat as only one plate cooler.