Constant-velocity universal joint

In a constant velocity universal joint in which two types of groove portions whose opening directions of included angles of balls are opposite to each other are alternately provided around a center line, a holder is rotated more smoothly on the basis of an extrusion load of the balls due to the included angles. Since the absolute value of the included angle (alpha) of the first groove part (30) inthe reference state in which the joint angle is 0 degree is greater than the absolute value of the included angle (beta) of the second groove part (32), the pressing load (Fa) of the ball (24) due tothe included angle (alpha) of the first groove part (30) is increased. Thus, in a region where a sufficient joint angle of the extrusion load (Fa) cannot be obtained due to the included angle (alpha)of the existing first groove portion (30), the joint angle of the first groove portion (30) is larger than the joint angle of the existing first groove portion (30) in the vicinity of 20 degrees at the time of recovery after b