To solve a conventional problem and to provide a structure allowing easy maintenance and facilitating replacement of a broken oil seal or bearing and the like by newly providing a parting plane almost in the center of an axle case and by removing an outer divided axle case from a transmission case.

The construction is such that a drive shaft 28 is supported with the axle case 23 fixedly provided on a side surface of the transmission case 22. The axle case is constructed so that the axle case 23 is formed with the parting plane in an axial middle part and can be divided into the outer divided axle case 23A and an inner divided axle case 23B.