Congenital quadricuspid aortic valve is a rare cardiac malformation with an unknown risk of infective endocarditis. We report a case of quadricuspid aortic valve complicated with infective endocarditis. A 53-year-old Japanese woman was hospitalized with leg edema and a fever of unknown origin. Corynebacterium striatum was detected in the blood culture. Echocardiography demonstrated a quadricuspid aortic valve with vegetation and severe functional regurgitation. The condition was diagnosed as a quadricuspid aortic valve with infective endocarditis, for which surgery was performed. The quadricuspid aortic valve had three equal-sized cusps and one smaller cusp (type B according to Hurwitz classification). We dissected the vegetation and infectious focus and implanted a mechanical valve. Following the case report, we review the literature.