powder are carried out in a conditions insulated from the atmospheric air the used atomizing medium 6 which collects in the granulation tank 5 is withdrawn through a discharge pipe 11c then circulated by a circulation pump 15 through a thickener 8 a filter 12 and a cooler 10 and then mixed with a freshly supplied atomizing medium and put to use in the meantime the metal powder is removed from the granulation tank 5 by means of a classifier 7 and then received in a hopper 18 in the hopper part of the atomizing medium adhering to the metal powder is separated placed in a storage tank 20 and returned via a circulation pump 15 39 to the thickener 8 the atomizing medium remaining on the surface of the metal powder is thoroughly removed in the next step in the embodiment illustrated in fig2 a fluidized bed furnace 24 is used for this step the metal powder which has departed from the hopper 18 of fig1 is released in a flow rate adjusted by a valve 17a onto a belt conveyer 19 scooped in a bucket elevator 21 and delivered to an upper hopper 22 forwarded in a prescribed amount adjusted by a valve 17b through a screen feeder 23 and introduced into a fluidized bed furnace 24 the fluidized bed furnace 24 is capable of simultaneously the gasification and separation of the used atomizing medium and the heat treatment of the metal powder the upper two stages of the fludized bed furnace are used for the step of separation and the third stage for the step of heat treatment by 26 is denoted indirect heating means for ensuring supply of heat necessary for the.