The present invention relates to a transmission device, and more particularly to a transmission device which automatically shifts gears without a clutch. The transmission device according to one aspect of the present invention comprises: an input shaft for receiving rotational force from the outside; a torque converter provided at the input shaft; a power gear which is rotated by the torque converter; an output gear which is coupled with the power gear to revolve and/or rotate by the power gear; a gearshift which is coupled with the output gear to allow idle rotation or to generate a rotational load; and a carrier which is rotated according to the revolution of the output gear.
