The present invention provides a composition which may be ingested orally in a small dose for the purpose of improving brain function, and a method for improving brain function. The present invention is a composition for improving brain function, the composition comprising, as an active ingredient, X-Met-His-Gln-Pro-His-Gln-Pro-Leu-Pro-Pro-Thr-Val-Met-Phe-Pro-Pro-Gln-Ser-Val-Leu or a salt thereof, wherein X is absent or represents Ser-Trp or Leu-Gln-Ser-Trp.
