The present invention relates to a pharmaceutical composition and a food composition containing Portulaca grandiflora Hook. extract or a fraction thereof as an active ingredient for preventing, treating or ameliorating neuroinflammation or neuro-degenerative diseases. The Portulaca grandiflora Hook. extract or a fraction thereof according to the present invention is derived from a natural product which has been in use as a natural medicinal ingredient, and as such, has no side effects and inhibits expression of NO, PGE 2 , iNOS and/or COX-2 genes or protein, which are factors associated with inflammation, and is additionally superbly effective for increasing and improving memory and the ability to learn, and thus can be beneficially used to prevent or treat neuroinflammation or neuro-degenerative diseases.