Disclosed is a constant velocity universal joint, comprising: an outer joint member (10) in which at least one end portion is open; an inner joint member (20) for transmitting torque together with the outer joint member (10) through balls (30) under a state in which angular displacement is allowed; a boot (70) for closing an opening portion of the outer joint member (10), the boot (70) having a small diameter end portion (72) fitted onto a shaft (50) extending from the inner joint member (20); a lip portion (75) abutting on an outer peripheral surface of the shaft (50); and a ventilation groove (76) for establishing communication between an inside and an outside of the boot (70), the lip portion (75) and the ventilation groove (76) being formed in an inner peripheral surface of the small diameter end portion (72) of the boot (70).