An in-wheel motor drive device speed reducer includes an input shaft coupled to a motor rotating shaft. an output shaft coupled to a wheel hub and parallel to the input shaft, and one or more intermediate shafts parallel to the input shaft and the output shaft. An input gear coupled to the input shaft, a plurality of intermediate gears coupled to the intermediate shafts, and an output gear coupled to the output shaft mesh with each other and configure a drive transmission path leading to the output gear from the input gear through the plurality of intermediate gears. When viewed axially using the intermediate shaft, axes of the output shaft, the at least one intermediate shaft, and the input shaft are arranged in this order in the vehicle front-to-rear direction. The axis of the at least one intermediate shaft is disposed above the axes of the output and input shafts.