An object of the present invention is to find a component that is safe and is capable of effectively exerting various effects such as prevention or amelioration of diabetes, prevention or amelioration of metabolic syndrome, amelioration of insulin resistance, inhibition of an increase in a postprandial blood sugar level, and inhibition of α-glucosidase activity. The present invention provides agents for preventing or ameliorating diabetes or the like, the agents including a component of a hybrid plant of Camellia sinensis and Camellia taliensis as an active ingredient. The hybrid plant is preferably Sun Rouge, and each of the agents preferably includes a tea leaf extract of the hybrid plant.
