A power generating device includes a carrier module, a stator module, a rotor module and a power generating module. The stator module is assembled to the carrier module, and has a first circuit board and a plurality of driving coils. The rotor module is located in an electromagnetic field, and has a multipolar magnetic rotor and a rotating axle. A magnetic field of the multipolar magnetic rotor interacts with the electromagnetic field to make the rotor module rotating relative to the stator module, and make the multipolar magnetic rotor producing a varying magnetic field. The power generating module is located in the varying magnetic field, and has a second circuit board and a plurality of induction coils. The induction coils induct the varying magnetic field to output an induction circuit to the second circuit board.