PROBLEM TO BE SOLVED: To provide a method for producing a chondroitin sulfate oligosaccharide, in particular, to provide a method for producing a homogeneous chondroitin sulfate oligosaccharide which is a hydrolysis product and an even-numbered oligosaccharide comprising a disaccharide having a sulfate group or an acetylamino group as a constitutional unit, wherein the method can inexpensively and industrially produce the chondroitin sulfate oligosaccharide regardless of the structure of chondroitin sulfate, particularly even in the case of using chondroitin sulfate mainly having glucuronic acid-N-acetyl-D-galactosamine 6-sulfate structure as a starting material, and to provide food, cosmetics and a pharmaceutical composition containing a chondroitin sulfate oligosaccharide produced by the method.SOLUTION: The present invention relates to a method for producing a chondroitin sulfate oligosaccharide which is an even-numbered oligosaccharide comprising a disaccharide having a sulfate group and/or an acetylamino group as a constitutional unit.
