Disclosed herein is a driving device of armature balance machine, in which a driving motor is formed on the same centerline of the armature, a hinge block pivot-connected by the hinge shaft is installed in the finger mounter of the bracket in such a manner that the hinge shaft is disposed on the same centerline of the driving motor and the variable roller is formed at one side of the hinge shaft, the finger provided with a complementary roller is symmetrically constructed about the centerline of the driving motor, and thereafter a belt is wound around each roller, so that the construction of the driving motor can be simplified and thus the length of the belt is minimized and the vibration of the belt is minimized, thereby enabling to keep the tension applied to the belt in an optimum state, due to the facts that the tension of the belt is symmetrical about the centerline of the belt and also the variable roller i.e. the tension adjusting means is not operated by the belt.