PURPOSE: To provide a method for efficiently removing lignin from a plant feedstock in a short time.

CONSTITUTION: This method for removing lignin from a plant feedstock is such that a unit process made up of a treatment step to use an enzyme acting on lignin and a washing step using an alkali is repeated at least once. In this case, the former step is conducted by limiting the rise in the whiteness of the feedstock defined by the formula described below to 5 points or smaller: [rise in whiteness (point)] = [the whiteness (%) after the former step] -[the whiteness (%) before the former step].