NOVELTY - The methane fermentation apparatus has cylindrical portions (11,21,31), raw material heating portion (10), acid generation portion (20), methane fermentation portion (30), desulfurizing portion (40), float tank (51) and specific units. Portion (10) carries out heating of organic waste to temperature (38-55degreesC) suitable for acid generation and fermentation. Portion (40) removes hydrogen sulfide from biogas generated by fermentation.    USE - The apparatus is useful for methane fermentation of raw material, such as livestock manure and organic refuse.    ADVANTAGE - The methane fermentation apparatus is compact and economical, and ejection of bad smell from the system is prevented. The generation amount of methane gas is increased.    DETAILED DESCRIPTION - The methane fermentation apparatus has three cylindrical portions (11,21,31) in common axis. The apparatus has raw material heating portion (10) having air supply portion (13) in lower portion, acid generation portion (20) formed as annular ring portion between portions (11,21), methane fermentation portion (30) formed as annular ring portion between portions (21,31), desulfurizing portion (40), float tank (51) and units (A-E). The portion (10) carries out heating of organic waste as raw material to temperature (38-55degreesC) suitable for acid generation and methane fermentation. The unit (A) prevents the sludge deposition in raw material heating portion by supplying air and forming air lift. The unit (B) carries out flow of heated raw material overflowed from heating portion to acid generation portion. The unit (C) retains raw material discharged from acid generation portion in methane fermentation portion, and carries out fermentation of raw material. The unit (D) prevents the sludge deposition in bottom portion of acid generation portion using a conical slope. The desulfurized portion is provided at upper portion of acid generation portion and methane fermentation portion. The unit (E) carries out anaerobic fermentation of raw material in methane fermentation portion equipped with methane bacterium supporter, and methane gas is produced. The desulfurizing portion carries out removal of hydrogen sulfide from biogas generated by fermentation. The float tank retains biogas containing methane ejected from desulfurized portion, and is provided in upper portion of desulfurized portion. The float tank is installed in a float tank cover (52). A gas retention unit (50) attached with float tank guide portion (52a) is provided in the top portion of float tank. The offensive odor component contained in biogas is not ejected out of the system.    DESCRIPTION OF DRAWING(S) - The figure shows the longitudinal cross-sectional view of methane fermentation apparatus.    Raw material heating portion (10)    Cylindrical portions (11,21,31)    Warm water jackets (11a,21a)    Raw material supply portion (12)    Air supply portion (13)    Acid generation portion (20)    Methane fermentation portion (30)    Desulfurizing portion (40)    Gas retention portion (50)    Float tank (51)    Float tank cover (52)    Float tank guide (52a)