PURPOSE: To simplify constitution of a transmission case with a grand speed governor mechanism and to prevent the influence of an inertia amount of a governor rotation body from being exercised on the gear on the synchronized side of a synchronous engagement device.

CONSTITUTION: In an axle drive device wherein an input shaft 2 to which a power is inputted from an engine, a pair of axles 1L and 1R, a differential gear device D, and a power transmission mechanism to interconnect the input shaft and the differential gear device are contained in a common transmission case M, the shaft end of the input shaft 2 in a power transmission mechanism is exposed to the outside of the mission case, and the governor shaft 17 of a grand speed governor mechanism G interlocked and linked to an engine throttle valve is separably coupled to the input shaft 2. A governor case 6 to contain the mechanism G is formed removably from the mission case M. The governor rotation body 15 of the mechanism G is engaged with the gear 14 on the synchronous side of a synchronous engaging device contained in the power transmission mechanism.