The present invention relates to a pumping device using vapor pressure for supplying water for a power plant, which uses the vapor pressure that is stored in a vapor generator used in the power plant to more quickly and readily supply water to the vapor generator without separately using a high-capacity pump and a condenser. The present invention is characterized by significantly saving equipment cost, because various high-capacity pumps and condensers are not required at all, enhancing energy efficiency and operability by eliminating unnecessary power consumption that is used to operate same, reducing maintenance costs, and actively and efficiently preserving nature and the environment by fundamentally eliminating hot water and sewage, which are byproducts of nuclear or thermal power generation, that are discharged into the ocean without treatment.