The invention discloses a device for treating waste. The device comprises a smelting furnace and a combustion furnace; a first feeding opening is formed in the upper portion of the side wall of the smelting furnace, a slag discharging opening is formed in the bottom of the side wall of the smelting furnace, a lower heating source is arranged on the lower portion of the smelting furnace, and is located above the slag discharging opening, a top heating source is arranged on the top of the smelting furnace, and the height of the smelting furnace ranges from 2 meters to 5 meters. The combustion furnace is communicated with the side wall of the upper middle portion of the smelting furnace, an auxiliary heating source is arranged on the lower middle portion of the combustion furnace, and a smokeoutlet is formed in the top; energy consumption can be reduced, meanwhile, through reduction of the height of the smelting furnace, the top and the side face can be heated at the same time, in addition, complete decomposing of dioxin is achieved, and emissions of the dioxin can be controlled.