To find a driving source from natural fluid, solar energy and the like to obtain heat generation therefrom, and to store and use a large amount of hot-water of high temperature by means of a heat medium to allow all of living beings on the earth to live together long.

This hot-water device generates the heat by getting the torque from the wind, the water flow, the sunlight, the heat and the like, stores the heat in a variable-mass heat medium, and heats the water to store the hot-water, so that a small amount of hot water is used in bathing and domestic affairs, and a large amount of hot water is used for agriculture, stockbreeding, gardening, air-conditioning and sightseeing. As the flame is not used, the fire and the air pollution can be prevented and the new energy can be achieved.