PROBLEM TO BE SOLVED: To provide an erythrocyte function improving agent that has both high antioxidation effect and excellent migration ability to erythrocytes and is capable of effectively protecting erythrocytes against an oxidation stress.SOLUTION: The present invention provides a medicine comprising as an active ingredient carotenoid cucurbitaxanthin A and/or a derivative thereof, wherein the carotenoid cucurbitaxanthin A is (3S,3'R,5R,6R)-3,6-epoxy-5,6-dihydro-β,β-carotene-3',5-diol with 3,6-epoxy endo group at a terminal, and has antioxidation effect.SELECTED DRAWING: None【課題】高い抗酸化作用と、高い赤血球への移行能とを兼ね備え、赤血球を酸化ストレスから効果的に保護できる赤血球機能向上剤の提供。【解決手段】末端に3,6-エポキシエンドグループを有し、（３Ｓ，３'Ｒ，５Ｒ，６Ｒ）－３，６－エポキシ－５，６－ジヒドロ－β，β－カロテン－３'，５－ジオールである、抗酸化作用を有するカロテノイドククルビタキサンチンＡ及び／又はその誘導体を有効成分とする医薬。【選択図】なし
