A rotation transmitting apparatus comprises a first sun gear joined to a first shaft so as to rotate interlockingly, a second shaft arranged to the first shaft coaxially, a second sun gear joined to the second shaft so as to rotate interlockingly, a first planetary gear meshed with the first sun gear, a second planetary gear rotating with the first planetary gear and meshed with the second sun gear, and a carrier supporting the first and second planetary gears and arranged to be driven by a differential electric motor. In particular, the number of teeth of each of the first and second sun gears and the first and second planetary gears is determined so that the ratio of a torque applied to the second shaft to a torque applied to the first shaft ranges from 1:0.7 to 1:0.9.