Provided is a vibration-reduction mechanism for a gear cutting machine capable of reducing mechanical vibrations in the gear cutting of a helical gear by selecting an optimal balancer weight. For this purpose, provided is a vibration-reduction mechanism for a gear cutting machine that performs gear cutting on a workpiece (W) with a cutter (T) attached to a main shaft (26) made to move reciprocally by a crank. The vibration-reduction mechanism includes balancer shafts (16 and 17) arranged in parallel to a crank shaft (15). The balancer shafts (16 and 17) rotate synchronously with the crank shaft (15) at the same speed as the speed of the crank shaft (15). The balancer shaft (16) rotates in the opposite direction to the rotational direction of the crank shaft (15) while the balancer shaft (17) rotates in the same direction as the rotational direction of the crank shaft (15). The vibration-reduction mechanism also includes: main balancer weights (41 and 42) detachably attached onto the crank shaft (15) so as to reduce vibrations in the axial direction of the main shaft (26); and sub balancer weights (43 to 46) detachably attached onto the balancer shafts (16 and 17) so as to reduce vibrations in directions that are orthogonal to the axial direction of the main shaft (26). The balancer weights (41 to 46) are selected on the basis of a stroke width of the main shaft (26) and on the basis of a lead corresponding to the helical angle to be formed in the workpiece W.