To provide a production method of a water-soluble fraction of beer lees, by which the water-soluble fraction of beer lees can easily be obtained efficiently at a low cost in high yield and to provide the water-soluble fraction of beer lees to be obtained by the production method.

The production method of the water-soluble fraction of beer lees comprises a step of bringing beer lees into contact with water at 150-220°C, preferably, at 160-200°C under the pressure lower than the saturated vapor pressure at this temperature for 10-30 minutes, preferably, for 15-20 minutes. The water-soluble fraction of beer lees is used as a raw material of methane fermentation.