Abstract: A two-speed transmission including: a sun gear configured to be rotated by an external driving force; a planet gear arranged around the sun gear; a ring gear having a gear train; a first clutch configured to be engaged with the sun gear to be restrained by the sun gear if the sun gear is rotated in a first direction; a second clutch configured to be engaged with the ring gear to be restrained by the ring gear if the sun gear is rotated in a second direction; and a carrier configured to receive a driving force from the sun gear by restraint of the first clutch to be driven in a first reduction gear ratio or to receive a driving force that is transferred through the sun gear, the planet gear, and ring gear by restraint of the second clutch to be driven in a second reduction gear ratio.