To improve the utilization efficiency of consumed power by dividing the heaters of a heating tank into a plurality of parts and respectively decreasing the supply of electric current to the divided heaters in accordance with the decreased volume of garbage.

While garbage with which a heating tank 4 is charged is ground and agitated by rotating agitating members 5, its water is gradually evaporated under the heat of a heater 6 and its weight and volume are decreased. Remaining solid substances are taken out from a take-out port 16, steam B is divided into condensate W and gas G by a condenser 12 and the condensate W is stored once in a tank 17 and successively exhausted outside. The gas G is heated to high temperature by a deodorizing heater 13, undergoes a heat exchange with new air A with its temperature lowered and is released to atmospheric air. The heater 6 of the heating tank 4 of a garbage drying and treatment device 1 is divided into an upper heater 6a and a lower heater 6b. A control means 36 independently supplies electric current to the upper heater 6a and the lower heater 6b and decreases the number of times of supply of electric current in accordance with the reduced volume of garbage.