A plunging type constant velocity universal joint includes an outer joint member, an inner joint member, eight balls, and a cage. A curvature center of a spherical portion of an outer peripheral surface of the cage and a curvature center of a spherical portion of an inner peripheral surface of the cage are offset to opposite sides in the axial direction with respect to a joint center by an equal distance. A ratio PCDBALL/DBALL of a pitch circle diameter PCDBALL of the balls to a diameter DBALL of each of the balls is set from 3.3 to 3.6. A ratio TI/DBALL of a radial thickness TI of the inner joint member to the diameter DBALL of each of the balls is set from 0.30 to 0.45.