(EN) The present invention provides a method for producing a sugar liquid from a cellulosic biomass material, which sugar liquid has improved fermentability. The present invention is a method for producing a sugar liquid comprising the steps of: adding an alkali(s) to a concentrated cellulosic biomass sugar liquid to adjust the pH to not less than 7, so as to precipitate an insoluble substance(s) containing at least magnesium; and performing filtration through a microfiltration membrane to remove the insoluble substance(s), to obtain a sugar liquid as a permeate. Figure 1.