PURPOSE:To utilize for manufacturing a gear which is required to have a particularly high accuracy by a constitution wherein of motions to be given to a saddle sliding base, even if a quantity is small, a motion receiving an influence of a stick slip is generated smoothly without depending upon the sliding of a work saddle on the saddle sliding base. CONSTITUTION:The device consists of a bed 1, a saddle sliding base 2 and a work saddle 3, etc. of a gear cutting machine tool. Further, a gear to be machined 4 is supported by the saddle 3 through a work support 5 and a work table 6 on the saddle 3. Further, a tool 7 for performing a creation working of a gear 4 and a guide part 9 of a saddle 8 are installed on a tool saddle 8. Next thereto, the motion of the saddle 3 is given while leaf springs 13, 14 are being deflected and the motion of the saddle 3 is faithful to the shape of an operational surface 24 of a cam 20 and very flexible and smooth and a gear having an exact tooth trace (a gear for which a crowning working is applied) is obtained. With this, contribution can be made to a manufacture of a gear which is required to have a particularly high accuracy.