This variable electric motor system comprises an electrically powered device and a planet gear transmission device. One of a sun gear shaft, a planet gear carrier shaft, and an internal gear carrier shaft of the planet gear transmission device constitutes an output shaft, another shaft constitutes a constant-speed input shaft, and the other shaft constitutes a variable-speed input shaft. The electrically powered device includes: a constant-speed electric motor including a constant-speed rotor that rotates about the axis, and that is connected to the constant-speed input shaft; and a variable-speed electric motor including a variable-speed rotor that rotates about the axis, and that is connected to the variable-speed input shaft. The variable-speed rotor has a shaft insertion hole formed therethrough in the axial direction, the shaft insertion hole having a cylindrical shape centered on the axis. The constant-speed rotor is inserted through the shaft insertion hole.