NOVELTY - Methane generating device contains flow-down anaerobic colander and flow-up anaerobic fermenting pot, where a liquid duct is equipped between discharging opening of the colander and upper charging opening of the fermenting pot. Discharging opening valve, liquid transfer-pump and charging opening valve are mounted on the duct. The ends of circumfluence tube are respectively connected to part of the flow-down anaerobic colander and the duct. The fermenting pot discharging circumfluence tube is connected to discharging opening of the flow-up anaerobic fermenting pot.    USE - The device is useful for generating methane (claimed), and for utilizing biomass energy.    ADVANTAGE - The device has high efficiency in gas production, and is simple, fast in anaerobic fermentation process and convenient.    DETAILED DESCRIPTION - Methane generating device contains flow-down anaerobic colander and flow-up anaerobic fermenting pot, where a liquid duct is equipped between lower discharging opening of the flow-down anaerobic colander and upper charging opening of the flow-up anaerobic fermenting pot. The discharging opening valve, liquid transfer-pump and the charging opening valve are orderly mounted on the liquid duct, in which the discharging opening valve is on one side of the flow-down anaerobic colander, and the charging opening valve is on one side of the flow-up anaerobic fermenting pot. Upper and lower ends of the circumfluence tube are respectively connected to the opening on upper part of the flow-down anaerobic colander and the liquid duct, lower part of the circumfluence tube and the connecting point of the liquid duct are located between the liquid transfer-pump and the charging opening valve, returning valve and the charging valve of the circumfluence tube are respectively mounted on upper end and lower part of the circumfluence tube. Upper side end and lower side end of the fermenting pot discharging circumfluence tube are respectively connected to the upper discharging opening and lower discharging opening of the flow-up anaerobic fermenting pot, and the bottom end of the fermenting pot discharging circumfluence tube is connected to the liquid duct which is set between 12-16. Upper discharging opening valve, lower discharging opening valve, and head valve of the fermenting pot discharging circumfluence tube are respectively placed on upper side end, lower side end and bottom part of the fermenting pot discharging circumfluence tube.