An object of the present invention is to provide an agent for improving red blood cell function which has both high antioxidant action and high ability to migrate into red blood cells, and can effectively protect red blood cells against oxidative stress. Cucurbitaxanthin A and/or a derivative thereof has an ability to migrate into red blood cells significantly higher than that of the other carotenoids reported to migrate into red blood cells, and can effectively protect red blood cells against oxidative stress, and thus, is effective as an agent for improving red blood cell function.
