Abstract: Provided is a fluidized bed furnace for heating waste to extract a combustible gas from the waste, including: a plurality of wind boxes arranged on a lower side of a bottom wall of a furnace body to blow a fluidizing gas into the fluidized bed; a plurality of temperature detection sections disposed at respective positions allowing detection of temperatures of an upper position and a lower position vertically spaced in a first region, and allowing detection of temperatures of upper and lower positions vertically spaced in a second region; and a control section operable, based on the temperatures detected by the temperature detection sections, to adjust an air ratio of the fluidizing gas to be fed to each of the wind boxes, so that the temperature of the fluidized bed is raised in a direction from the first region toward the second region.