than the attenuation of conventional reduction gears having no vibration damping and sound absorbing means since the reduction gear of the present invention is constructed in the above described manner the following advantages are obtained arrangement of laminated vibration damping and sound absorbing steel sheets inside of the inner wall of the casing can prevent sound generated by meshing engagement of the respective gears from being transmitted to the casing in addition splash and drops of a lubricant scattered from the rotating gears will not collide with the casing due to the arrangement of the laminated vibration damping and sound absorbing steel sheets thus leakage of the sound out of the casing can be reduced remarkably in other words the sound can be attenuated by a quantity of about 5 to 10 db a compared with the conventional reduction gear further since there is no need to secure a sound proofing material to the outer wall of the casing the reduction gear itself can be designed with smaller dimensions additionally since a known design of fitting bearings into the side wall of the casing can be employed for the reduction gear the latter can be constructed without the necessity of changing the present dimensions of the casing of course the present invention may utilize any number of shafts and gears arranged for reduction or other purposes for example the present invention has been explained along the reduction gear but the present invention may be applied to any gear device e g a speed increase gear also in the drawing the casing of the gear device is.