<p>The present invention relates to a constant velocity joint, and more specifically, to a constant velocity joint which increases a force acting in an inward direction of an outer wheel if torque is applied in a bent state, and improves a structure of a cage and a cup unit which can resist the force acting in the inward direction of the outer wheel in response to an increase in force to realize operational stability and structural stability. The constant velocity joint according to the present invention comprises: an outer wheel comprising a cup unit having an accommodation space therein and a plurality of outer grooves separated from an inner surface of the cup unit and formed in a curved shape; an inner wheel accommodated in the outer wheel and provided with inner grooves formed on an outer surface thereof in a curved shape corresponding to the outer grooves; a plurality of balls accommodated in the inner grooves and the outer grooves; and a cage comprising a window which is disposed between the outer wheel and the inner wheel and defines position of the balls. A part thickness between an inner end of the cage and the window is thicker than a part thickness between an outer end of the cage and the window.</p>
