To provide a method for producing an anti-inflammatory agent exhibiting high pharmacological activity, no side effect, and high safety by using natural products as raw materials.

The method for producing an anti-inflammatory agent for external use comprises a step for obtaining a hydrolysis-treated liquid containing a xylo-oligosaccharide/lignin complex by subjecting a chemical-pulp-derived lignocellulose material to a hydrolysis treatment with hemicellulase; a step for obtaining a xylo-oligosaccharide/lignin complex concentrated liquid by eliminating a low-polymerization-degree oligosaccharide and low-molecular-weight foreign substances from the hydrolysis-treated liquid; a step for obtaining a dilute acid-treated liquid containing an acidic xylo-oligosaccharide and a neutral xylo-oligosaccharide by treating the xylo-oligosaccharide/lignin complex concentrated liquid with a dilute acid to liberate, condensate, precipitate, and remove a lignin-like matter; a step for obtaining a refined xylo-oligosaccharide condensed liquid containing a mixture of an acidic xylo-oligosaccharide and a neutral xylo-oligosaccharide by subjecting the dilute acid-treated liquid to a filtration-decoloration treatment; a step for obtaining an acidic xylo-oligosaccharide composition having an average degree of polymerization of 2.0-11.0 from the refined xylo-oligosaccharide concentrated liquid by an adsorption treatment using a weak anion-exchange resin; and a step for incorporating the acidic xylo-oligosaccharide composition having an average degree of polymerization of 2.0-11.0 into an anti-inflammatory agent base.