Abstract: This invention is directed to a gaseous fuel containing water produced by a process, wherein a mixture gas of water, fuel and air is swirled with intense friction between them, contacted with metallic elements to receive thermoelectrons and activated at a temperature about 100.degree.-600.degree. C., as well as a process and apparatus for producing said fuel. When the gaseous fuel containing water by this invention is burned, the calorific value is greater than that of pure fuel combustion and the discharge of NO.sub.x and CO from the exhaust gas is small.