A wind turbine generator that is capable of completely eliminating heater heating of lubricating-oil piping or that is capable of reducing the number of heater heating locations to the minimum requirement is provided. A wind turbine generator is provided with a lubricating system that circulates lubricating oil (L) in a lubricating-oil storage tank through lubricating-oil piping connected to a lubricating-oil pump, to lubricate a main bearing connected to the lubricating-oil piping by supplying the lubricating oil (L) thereto. This lubricating system is provided with a lubricating-oil recovery line that is formed when the lubricating-oil pump is stopped and in which the lubricating oil (L) falls naturally and is recovered in the lubricating-oil storage tank.