A ball type constant velocity joint comprising: an outer race formed to a cylindrical shape with an opening portion on at least one axial side and formed with a plurality of outer race ball grooves on an internal surface thereof; an inner race arranged inside the outer race and formed with a plurality of inner race ball grooves on a peripheral surface thereof; a plurality of balls that roll on the respective outer race ball grooves and the respective inner race ball grooves and that transmit a torque between the outer race and the inner race ; and a cage formed annularly, arranged between the outer race and the inner race , and formed with a plurality of window portions that respectively receive balls in a circumferential direction thereof; wherein on at least one of a plurality of groove wall protrusions that are configured by sidewall surfaces of the inner race ball grooves adjoining, cutouts are respectively formed on axially opposite sides of the inner race on a peripheral side of the inner race , characterized in that on the one axial side of the inner race , a center locus of the ball when the ball rolls on the inner race ball groove is set to a circular arc; the cutout on the one axial side is formed so that a contact point locus between the inner race ball groove and the ball is set at an axial position where the cutout on the one axial side is formed, an axial position where the cutout on the other axial side is formed is set on the other axial side beyond the contact point locus between the inner race ball groove and the ball at the time of a torque transmission, and a radially inward bottom portion of the cutout on the other axial side is set to be located radially inside beyond an extension line of the contact point locus between the inner race ball groove and the ball. an outer race formed to a cylindrical shape with an opening portion on at least one axial side and formed with a plurality of outer race ball grooves on an internal surface thereof; an inner race arranged inside the outer race and formed with a plurality of inner race ball grooves on a peripheral surface thereof; a plurality of balls that roll on the respective outer race ball grooves and the respective inner race ball grooves and that transmit a torque between the outer race and the inner race ; and a cage formed annularly, arranged between the outer race and the inner race , and formed with a plurality of window portions that respectively receive balls in a circumferential direction thereof; wherein on at least one of a plurality of groove wall protrusions that are configured by sidewall surfaces of the inner race ball grooves adjoining, cutouts are respectively formed on axially opposite sides of the inner race on a peripheral side of the inner race , characterized in that on the one axial side of the inner race , a center locus of the ball when the ball rolls on the inner race ball groove is set to a circular arc; the cutout on the one axial side is formed so that a contact point locus between the inner race ball groove and the ball is set at an axial position where the cutout on the one axial side is formed, an axial position where the cutout on the other axial side is formed is set on the other axial side beyond the contact point locus between the inner race ball groove and the ball at the time of a torque transmission, and a radially inward bottom portion of the cutout on the other axial side is set to be located radially inside beyond an extension line of the contact point locus between the inner race ball groove and the ball. <EOS>