Abstract: A housing cannot be made compact by only securing a space corresponding to a reservoir tank at the upper part of the housing, and the space at the upper part of the housing cannot be utilized if the reservoir tank is integrally provided to the upper part of the housing. An axle driving apparatus comprising a tubular reservoir tank erected on the upper surface of the upper wall surface of the housing for accommodating an HST, wherein, since the reservoir tank is thinly elongated and is freely bendable, it can be disposed in a limited space. The housing is divided into a first room and a second room with which the reservoir tank communicates. Further, a first magnet is disposed at a position where the first and second rooms are connected, and a second magnet is disposed in the proximity of an oil filter connected to a closed circuit of the HST so that impurities can be removed.