To heat and sterilize waste in a bag by circulating high pressure hot blast and simultaneously reduce the volume of the waste by melting and softening the waste and then pressing the same.

This treatment apparatus is formed by a vertical movable plate disposed on the upper part of a bucket conveyer and the heat treatment part for fixing an air supply pipe and an exhaust pipe having small holes on the peripheral surfaces thereof and a presser for putting in and out the air supply and exhaust pipes from the bottom to vertically move the vertically movable plate. This heat treatment part is provided with a first heating part for heating the bucket from the side, a second heating part for heating the same from below and a third heating part for heating the same from above. The waste in the bag is compressed by the presser, and high pressure hot blast generated by a hot blast blow-in device is blown from the supply pipe inserted in the bag by pressing down the movable plate to thereby heat and sterilize the waste, and reduce the volume of the waste by heating, melting and pressing by the presser.