Provided is a transmission device that can increase a lubricity of a bearing in a planetary gear. The present disclosure includes the transmission device including a sun gear, a ring gear, planetary gears, bearings through shafts of the planetary gears are inserted, a differential case including bearing holders holding the respective bearings, a differential mechanism arranged inside the differential case, and a gear case supporting the differential case in a rotatable manner. Each bearing holder includes a cylindrical part holding a corresponding one of the bearings, and a pocket that is recessed from a radially inner side to a radially outer side to have an internal space that axially overlaps with the corresponding one of the bearings. The gear case includes a protrusion that is arranged to overlap with the pockets from the radially inner side of the sun gear and that axially protrudes toward the bearings.

A drive device includes a motor, a motor shaft, a planetary gear mechanism in which the motor shaft is fixed to a sun gear, a differential gear in which a differential case is mechanically connected to a carrier, a first output shaft, a second output shaft, an inboard drive shaft fixed to the other end of the second output shaft, a differential limiting mechanism including ring-shaped clutch plates about a central axis of the second output shaft, and a casing. An outside diameter of the inboard drive shaft about the central axis is smaller than a bore diameter of the clutch plates. Part of the casing is disposed between the differential limiting mechanism and the inboard drive shaft, and covers the differential limiting mechanism. The casing has a recess on a surface that faces the inboard drive shaft. An end of the inboard drive shaft is positioned inside the recess.