PROBLEM TO BE SOLVED: To provide an arthralgia improving agent containing N-acetyl glucosamine as an active ingredient.SOLUTION: An arthralgia improving agent comprises N-acetyl glucosamine which is administered to a person to be administered in the amount of 10-400 mg/day. Preferably this amount is administered for at least four weeks, more preferably for at least eight weeks, still more preferably for at least 12 weeks. The arthralgia improving agent is preferably an agent for improving arthralgia without transformation, particularly a gonalgia improving agent. The BMI of a person to be administered exceeds 25 preferably. The age of a person to be administered is 20-49 years old preferably.
