PROBLEM TO BE SOLVED: To provide an anaerobic biological treatment method and an anaerobic biological treatment apparatus capable of stable treatment with high load in an anaerobic biological treatment of wastewater containing organic matters with a carbon number of 6 or less. SOLUTION: The anaerobic biological treatment apparatus 1 is used which includes a reaction tank 16 which ferments the wastewater containing the organic matters having the carbon number of 6 or less with methane under an anaerobic condition, and a membrane separator 26 that separates a treatment liquid obtained by the reaction tank 16 into sludge and treated water by a filter membrane, wherein a biological sludge concentration in the reaction tank 16 is adjusted to be within a range of 15,000-35,000 mg/L. COPYRIGHT: (C)2013,JPO&INPIT
