NOVELTY - Treated wastewater is made to flow from lower turbulent flow reaction layer (201) to the upper turbulent flow reaction layer (202) and laminar flow layer (3) which is formed on the upper turbulent flow reaction layer with the upward flow in the reaction tank, and thus methane fermentation of blanket type sludge is enabled.    USE - For methane fermentation of blanket type sludge such as organic wastewater from e.g. foodstuff industry, sewage and human waste.    ADVANTAGE - The method enables efficient, economical and rapid methane fermentation of wastewater, with suppressed amount of processing liquid. Bad effect by alkalinization is inhibited.    DETAILED DESCRIPTION - Treated wastewater is made to flow from lower turbulent flow reaction layer to the upper turbulent flow reaction layer and laminar flow layer which is formed on the upper turbulent flow reaction layer with the upward flow in the reaction tank, and thus methane fermentation of blanket type sludge is enabled. The turbulent flow reaction layer (2) retains the granule in turbulent flow state and is laminated in vertical state by more than 2 stage in the reaction tank. Water containing granule is returned to turbulent flow reaction layer, while making the clarified water of the treated water, containing granule subjected to upward flow form turbulent flow reaction layer of downward direction to the layer of upper direction, to overflow the tank. A vertical penetration pipe (4) for long and slender down flow from free water surface of the tank center to lower portion of tank, and penetration pipe (6) which pours water containing gas from the turbulent flow reaction layer of lower portion of tank to free water surface of tank center are provided.    An INDEPENDENT CLAIM is included for methane fermentation apparatus, which has methane fermentation tank (1) having more than 2 turbulent flow reaction layers laminated from downward direction, vertical penetration pipe, wastewater inflow pipe, and overflow weir (9).    DESCRIPTION OF DRAWING(S) - The figure shows the longitudinal cross-sectional view of the methane fermentation apparatus.    methane fermentation tank (1)    turbulent flow layers (2,201,202)    laminar flow layer (3)    penetration pipes (4,6)    overflow weir (9)    dividing walls (2011,2012)