NOVELTY - The apparatus has a fluid biomass feed pump that supplies fluid biomass (1). A confluence throwing-in pump (10) with which fluid biomass and non-fluidity biomass (2) are throw-in from fluid biomass feed pump is provided. A circuit (20) of a digested sludge which carries out circulation return of digested sludge extracted out from a digestion tank (30) is provided. A mixing throwing-in unit (23) is configured to throw in confluence liquid of fluid biomass sent from confluence throwing-in pump, and the non-fluidity biomass in circulation path containing circuit and digestion tank.    USE - Methane fermentation apparatus of biomass.    ADVANTAGE - Since the mixing throwing-in unit is configured to throw in confluence liquid of fluid biomass sent from confluence throwing-in pump, and the non-fluidity biomass in circulation path containing the circuit and the digestion tank, the digested-sludge solid substance density in the digestion tank is raised effectively without providing the excessive installation by mixing non-fluidity biomass and fluid biomass by the pump and pipe interior fundamentally. Thus, the sludge treating capacity of digestion step is heightened effectively.    DETAILED DESCRIPTION - The confluence storage tank is made to merge fluid biomass and non-fluidity biomass. The confluence throwing-in pump is connected to a lower opening of confluence storage tank. A temperature control unit with which the circuit and a crusher of sludge are equipped is provided. The solid substance density of the confluence liquid is adjusted by adjusting the flow volume of the fluid biomass. An INDEPENDENT CLAIM is included for a processing biomass method involves using thickened sludge of specific range of solid content concentration as non-fluidity biomass. The fluid biomass and the non-fluidity biomass are merged, so that flow volume of fluid biomass is three times or more of flow volume of non-fluidity biomass about fluid biomass and non-fluidity biomass. The digested sludge which extracted out the confluence liquid after confluence from digestion tank is supplied in the circuit of the digested sludge which carries out circulation return. The solid substance density of confluence liquid is adjusted by adjusting flow volume of fluid biomass.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the methane fermentation apparatus of biomass. (Drawing includes non-English language text)    Fluid biomass (1)    Non-fluidity biomass (2)    Confluence throwing-in pump (10)    Circuit of digested sludge (20)    Mixing throwing-in unit (23)    Digestion tank (30)