The present invention provides a speed reducer for a deviation drive device of a wind generator which uses lubrication grease lubrication instead of oil lubrication. The speed reducer (G1) for derivation drive device of wind generator is provided with multi-stage speed reduction mechanisms (40, 41) are is fixedly equipped on a wind power generation unit (1) so that a high-speed-grade speed reduction mechanism (40) is provided at the upper side and a low-speed-grad speed reduction mechanism (41) is provided at the lower side and furthermore an lubrication grease supplying opening (51) for supplying lubrication grease is provided for the high-speed-grade first speed reduction mechanism (40) is provided while the lubrication grease lubrication is performed in the first and the second speed reduction mechanisms (40, 41).