This technique provides a composition for improving a brain function. The composition comprises, as an active ingredient, an acetic acid and/or an acetate. Additionally, said improvement in a brain function is preferably associated with an alleviation of a cerebral function disorder or of a cognitive dysfunction. Additionally, the cognitive dysfunction is preferably Alzheimer's disease type dementia or vascular dementia. Additionally, the composition is preferably a composition for oral ingestion. Additionally, the composition is preferably a food and drink composition for improving a brain function.