Disclosed is a novel composition which has an effect of inhibiting or preventing angiogenesis, is applicable to the treatment, prevention or recurrence prevention of diseases associated with an angiogenic mechanism such as diabetic retinopathy and age-related macular degeneration, and is an alternative for physical therapies. Specifically disclosed are: an angiogenesis inhibitor comprising an inhibitor of CD9 that belongs to a four transmembrane protein family; and an anti-angiogenic composition comprising the angiogenesis inhibitor.