PURPOSE: To easily reduce a salt concn. in a biomass suspension by adding an alcohol to the biomass suspension to form an upper phase comprising a saltcontg. alcohol and separating this phase from a lower phase comprising the biomass.

CONSTITUTION: To a suspension contg. a biomass, esp. a liq. contg. a cell debris for obtaining a protein, an alcohol (pref., ethanol) is added to form an upper phase comprising a salt-contg. alcohol. This phase is separated from a lower phase comprising the biomass to extract the salt from the biomass suspension. The extraction of the salt is pref. conducted by mixing ingredients such that contents of the biomass suspension and the alcohol are 10 to 30 wt.% and 30 to 50 wt.%, respectively, remainder water.