The invention discloses a flameless combustion device. The flameless combustion device comprises a combustion-supporting wind spraying gun, a fuel spraying gun and a backflow ejector which are arranged in a hearth. The backflow ejector is provided with a backflow runner penetrating through the backflow ejector, and the inner diameter of the two ends of the backflow runner is larger than that of the middle of the backflow runner. A nozzle of the combustion-supporting wind spraying gun faces one end of the backflow runner. Based on the above content, strong internal circulation of smoke in the combustion device is realized, and the dilution effect on the concentration of oxygen in combustion-supporting wind is greatly improved through the ultra-high smoke circulation rate, so that the combustion reaction is slowed down. No obvious flame front exists in the combustion process, and the whole hearth is in a uniform temperature field. A high-temperature area higher than 1400 DEG C is not generated in the hearth, and therefore generation of nitric oxides is lowered to the maximum extent.