Provided is a fluidized bed device (3) including a fluidized bed (2) of a fluid medium that is formed in the interior of a fluidized bed container (1)by a gas, wherein the width of the introduction port (4a) of a throwing-in nozzle (4) which is connected to the upstream side end in the flow direction of the fluid medium in the longitudinal direction of the container (1) is equalized to the width of the fluidized bed (2), and the width of the discharge port (5a) of a drawing-out nozzle (5) which is connected to the downstream side end in the flow direction of the fluid medium in the longitudinal direction of the bed container (1) is equalized to the width of the fluidized bed (2).