To provide a ball-type constant velocity joint capable of miniaturizing a whole joint and reducing the weight by lessening the maximum load generated between a ball and a retainer.

A center locus C1 of a ball 40 rolling on an outer ring ball groove 23 is formed in an S shape curving circumferentially from one end to the other end of the outer ring ball groove 23 viewed radially and outwardly from an axis line of an outer ring 20. A center locus C2 of the ball 40 rolling on an inner ring ball groove 32 is formed in an S shape curving circumferentially from one end to the other end of an inner ring ball groove 32 viewed from a radially outer side to the axis line of the inner ring 30. When the ball 40 is positioned at a deeper side than the outer ring 20, a difference between a pitch circle radius of the outer ring ball groove 23 and a pitch circle radius of the inner ring ball groove 32 at a portion where the ball 40 is positioned is set greater than a difference at the portion where the ball 40 is positioned at a central position A.