To provide a garbage treatment device provided with a structure that can surely maintains fermentation/decomposition temperature at a prescribed temperature without incurring any increase in cost.

This device is provided with a reaction vessel 2 into which a material to be treated such as garbage, is charged, an agitation means for agitating the charged material to be treated and a heating means for maintaining the internal temperature of the reaction vessel 2 at a specified temperature, wherein: the reaction vessel 2 is fabricated so that its surface forms a part of the casing surface of a main body 1A of the device and a heat insulation panel 5 consisting of a combination of a heat-resistant and corrosion-resistant plate material positioned on the inner surface side of the reaction vessel 2 and a heat insulation material positioned on the outer surface side of the heat-resistant and corrosion-resistant plate material, is placed on the faces of the vessel 2.