A fluidized bed gasification furnace comprising: a plurality of air boxes installed in parallel; a fluidized bed formed by fluidizing a fluidization medium using combustion gas fed into the furnace via the air boxes; a plurality of temperature sensors detecting temperatures at different positions in the fluidized bed; a noncombustible discharge device that is installed below the fluidized bed; and a control device configured to identify a defective fluidization spot in which a low temperature spot is present in the distribution of the temperature obtained in the fluidized bed based on the distribution of the temperatures detected by the plurality of temperature sensors, said device is further configured to temporarily increase an amount of supplied combustion gas to the air boxes located below the identified defective fluidization spot, the plurality of temperature sensors include a first temperature sensor group having a plurality of temperature sensors (23,24,25) installed in a depth direction of the fluidized bed, including at least one temperature sensor located in the fluidized bed in the event of startup of the fluidized bed gasification furnace, and a second temperature sensor group (21,22) having a plurality of temperature sensors installed in a horizontal direction of the fluidized bed; the control device identifies the defective fluidization spot based on the temperature distribution of the depth direction which is based on results detected by the first temperature sensor group and the temperature distribution of the horizontal direction of the fluidized bed which is based on results detected by the second temperature sensor group; characterized in that the noncombustible discharge device has a pusher that discharges the fluidization medium discharged from the fluidized bed and mixed-in noncombustibles; the control device is configured to increase a speed of discharge of the noncombustibles and the fluidization medium discharged by the pusher; and the control device is configured to control the discharge speed of the noncombustibles by fixing forward and backward movement times of the pushes and changing a stop time of the pusher. a plurality of air boxes installed in parallel; a fluidized bed formed by fluidizing a fluidization medium using combustion gas fed into the furnace via the air boxes; a plurality of temperature sensors detecting temperatures at different positions in the fluidized bed; a noncombustible discharge device that is installed below the fluidized bed; and a control device configured to identify a defective fluidization spot in which a low temperature spot is present in the distribution of the temperature obtained in the fluidized bed based on the distribution of the temperatures detected by the plurality of temperature sensors, said device is further configured to temporarily increase an amount of supplied combustion gas to the air boxes located below the identified defective fluidization spot, the plurality of temperature sensors include a first temperature sensor group having a plurality of temperature sensors (23,24,25) installed in a depth direction of the fluidized bed, including at least one temperature sensor located in the fluidized bed in the event of startup of the fluidized bed gasification furnace, and a second temperature sensor group (21,22) having a plurality of temperature sensors installed in a horizontal direction of the fluidized bed; the control device identifies the defective fluidization spot based on the temperature distribution of the depth direction which is based on results detected by the first temperature sensor group and the temperature distribution of the horizontal direction of the fluidized bed which is based on results detected by the second temperature sensor group; characterized in that the noncombustible discharge device has a pusher that discharges the fluidization medium discharged from the fluidized bed and mixed-in noncombustibles; the control device is configured to increase a speed of discharge of the noncombustibles and the fluidization medium discharged by the pusher; and the control device is configured to control the discharge speed of the noncombustibles by fixing forward and backward movement times of the pushes and changing a stop time of the pusher.