To reduce the air pollution causing substances such as the PCDDs(polychlorinated- dibenzo-p-dioxins), contained in the waste gas of an incinerator at the time of incinerating the dead body of a small-sized animal to smaller values than legal control values by removing the air pollution causing substances.

Incineration equipment 2 is provided with an incinerator 21, a heat exchanger 24, a gas treatment facility, and a smoke and soot treatment facility. The incinerator 21 has three combustion chambers which are constituted in such a way that the waste gas produced in the first combustion chamber can be heated in the other combustion chambers so that unburned fly ash or organic matters may be burned completely. The heat exchanger 24 uses air for preventing the temperature drop in the incinerator 21 and as combustion air. The gas treatment facility is composed of three treatment columns 22a-22c, provided with a liquid regenerating tank 224, a filter 225, a cooler 227, etc., and sends the waste gas A from the incinerator 21 to the smoke and soot treatment facility in a dry state as a combustion gas A1 by quickly cooling and dehumidifying the gas A. In the smoke and soot treatment facility, the gas A1 is further dehumidified. The gas treatment facility is constituted in such a way that the facility can remove the air pollution causing substances contained in the combustion gas A by absorbing the substances into a processing solution.