A method of stopping combustion in a restrained combustion furnace in which wastes to be incinerated are gasified and then burnt with an air amount lower than a theoretical combustion air amount, in case of emergency, the method including steps of shutting off a combustion air supply line connected to the restrained combustion furnace, simultaneously feeding inert gas to lower portions and an outlet side of the furnace, and opening a bypass line connected to an upper portion of the furnace to flow gas in the furnace through a filter to a waste gas stack, thereby safely stopping the combustion in the restrained combustion furnace in case of emergency.