To provide a fluidized bed furnace which can stably produce iron carbide product having low reaction activity and extremely low possibility of reoxidation during transporting and storing.

In the fluidized bed furnace, in which the reaction is executed while fluidizing iron-containing powdery and granular raw material charged in the furnace with reaction gas introduced into the lower part in the furnace and the iron carbide product is discharged, the inner part in the fluidized bed furnace is divided into many chambers with partition plates 5 and a water spraying equipment or a low temp. reaction gas introducing equipment is provided in the fluidized bed in the divided chamber at the outlet side in the divided chambers divided into many chambers or at the lower part of the fluidized bed in the divided chamber at the outlet side.