PURPOSE: To improve the working accuracy and the efficiency by fixing and engaging a guide gear having a true involute tooth form and a gear to be guided having a corrected tooth form, to a tool shaft and a work shaft, subsequently, executing the working by bringing both the shafts close to each other.

CONSTITUTION: A tool shaft 5 and a work shaft 6 are placed in parallel, and also, a thread rolling tool 1 and a guide gear 3 having an uncorrected true involute gear are fixed at a prescribed interval W to the tool shaft 5. A gear to be guided 4 which is engaged to the gear 3, and a gear to be thread-rolled 2 is fixed at the same interval W to the work shaft 6. In this case, the gear to be guided 4 has a corrected tooth form which has formed a huge part 7 in its tooth top, engaged to the guide gear 3 and rotated. Subsequently, the shafts 5, 6 are brought close to each other relatively, and the working is executed until a backlash between the gears 3, 4 becomes zero. Since the working is executed based on the corrected tooth form, the working accuracy and efficiency are improved.