To burn a toxic gas and substance left unremoved by a conventional burner and generated when burning fossil fuel, and animal and plant oil, by combustion of enhancing gas which is a mixture of nontoxic hydrogen and oxygen at an economical rate at superhigh temperature.

A hydrogen mixed combustion method and a device are characterized by using both of the hydrogen and the oxygen or only the hydrogen provided by a hydrogen generator, as a combustion enhancer, by being supplied to the burner, by arranging the hydrogen generator on the front flow side of a boiler and a water heater.