A lapping device for gear helix artifact with equal common normal by rolling method, use the rotary table to accurately control the angle between the lapping surface of whetstone and the axis of the base-circle cylinder to control the helix angle of base-circle about the involute helicoid. Use the whetstone driven component to drive the whetstone to make a high-precision linear motion in the vertical direction to adjust the position of the lapping surface of whetstone. The distance between the two lapping surface of whetstone is precisely adjusted by the gauge block to control the processing length of the three tooth common normal of the gear helix artifact. The invention provides a lapping device for gear helix artifact with equal common normal by rolling method, it conforms to the generation principle of the involute helicoid, and there is no machining principle error.