An ionic liquid capable of dissolving lignin at a high level is developed, and a method for producing lignin from a biomass at low cost and safely using a simple apparatus is provided. The present invention provides a method for producing lignin, which comprises the steps of: (1) mixing a lignin-dissolving ionic liquid represented by chemical formula (1) (wherein R1 and R3 may be the same as or different from each other and independently represent an alkyl group having 1 to 6 carbon atoms or an alkenyl group having 2 to 6 carbon atoms, R2 may be mono- or poly-substituted and represents a hydrogen atom, an amino group, a hydroxy group, a phenyl group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms or an alkoxy group, Y represents CH2, O or S, n corresponds to the number of ring-constituting elements and is 1 or 2, and X represents an anion derived from an amino acid, wherein each of the alkyl group, the alkenyl group and the alkoxy group may have one or more atoms or gro
