A constant velocity universal joint includes an outer joint member in which at least one end portion is open, an inner joint member for transmitting torque together with the outer joint member through balls under a state in which angular displacement is allowed, and a boot for closing an opening portion of the outer joint member. The boot has a small diameter end portion fitted onto a shaft extending from the inner joint member, a lip portion abutting on an outer peripheral surface of the shaft, and a ventilation groove for establishing communication between an inside and an outside of the boot. The lip portion and the ventilation groove are formed in an inner peripheral surface of the small diameter end portion of the boot.