A power transmitting device comprising: an input side gear assembly including a first power input terminal and a plurality of first power output terminals; an output side gear assembly including a plurality of second power input terminals and a second power output terminal, the plurality of second power input terminals configured to operate based on power received from the plurality of first power output terminals of the input side gear assembly, respectively; and a stopper mechanism configured to block power transmission through one of two power transmitting paths (P1, P2) connecting the plurality of first power output terminals and the plurality of second power input terminals, wherein the input side gear assembly comprises: an input side sun gear, the input sun gear being the first power input terminal; an input side planetary gear connected to an outer circumferential surface of the input side sun gear, the input side planetary gear configured to rotate based on power received from the input side sun gear; and an input side carrier and an input side ring gear each connected to the input side planetary gear, the input side carrier and the input side ring gear each being one of the plurality of first power output terminals, wherein the output side gear assembly comprises: an output side sun gear and an output side ring gear connected to the input side carrier and the input side ring gear, respectively, the output side sun gear and the output side ring gear each being one of the plurality of second power input terminals; an output side planetary gear configured to engage with the output side sun gear and the output side ring gear; and an output side carrier connected to a rotation axis of the output side planetary gear, and the output side carrier being the second power output terminal, characterized in that the output side sun gear includes a compound gear having first external teeth configured to engage with the output side planetary gear, and second external teeth configured to receive power transmitted from the input side carrier, the second external teeth having a greater diameter than the first external teeth. an input side gear assembly including a first power input terminal and a plurality of first power output terminals; an output side gear assembly including a plurality of second power input terminals and a second power output terminal, the plurality of second power input terminals configured to operate based on power received from the plurality of first power output terminals of the input side gear assembly, respectively; and a stopper mechanism configured to block power transmission through one of two power transmitting paths (P1, P2) connecting the plurality of first power output terminals and the plurality of second power input terminals, wherein the input side gear assembly comprises: an input side sun gear, the input sun gear being the first power input terminal; an input side planetary gear connected to an outer circumferential surface of the input side sun gear, the input side planetary gear configured to rotate based on power received from the input side sun gear; and an input side carrier and an input side ring gear each connected to the input side planetary gear, the input side carrier and the input side ring gear each being one of the plurality of first power output terminals, an input side sun gear, the input sun gear being the first power input terminal; an input side planetary gear connected to an outer circumferential surface of the input side sun gear, the input side planetary gear configured to rotate based on power received from the input side sun gear; and an input side carrier and an input side ring gear each connected to the input side planetary gear, the input side carrier and the input side ring gear each being one of the plurality of first power output terminals, wherein the output side gear assembly comprises: an output side sun gear and an output side ring gear connected to the input side carrier and the input side ring gear, respectively, the output side sun gear and the output side ring gear each being one of the plurality of second power input terminals; an output side planetary gear configured to engage with the output side sun gear and the output side ring gear; and an output side carrier connected to a rotation axis of the output side planetary gear, and the output side carrier being the second power output terminal, an output side sun gear and an output side ring gear connected to the input side carrier and the input side ring gear, respectively, the output side sun gear and the output side ring gear each being one of the plurality of second power input terminals; an output side planetary gear configured to engage with the output side sun gear and the output side ring gear; and an output side carrier connected to a rotation axis of the output side planetary gear, and the output side carrier being the second power output terminal, characterized in that the output side sun gear includes a compound gear having first external teeth configured to engage with the output side planetary gear, and second external teeth configured to receive power transmitted from the input side carrier, the second external teeth having a greater diameter than the first external teeth.