To provide a power transmission device that can increase the range of speed variation between an engine and a power output shaft and effectively achieve reduction in size and cost of the device arrangement. The speed reduction ratios from an engine 1 to first output shaft 4c, 5c of first and second power distributors 4, 5 are different from each other. A speed change unit 10 is provided between the first output shaft 4c of the first power distributor 4 and a power output shaft 11 linked with driving wheels 2, 2 of the vehicle, and rotation transmission therebetween is achieved at a plurality of stages of speed reduction ratio. The rotation transmission from the first output shaft 5c of the second power distributor 5 to the power output shaft 11 is achieved via gears 20, 15b or rotation transmission mechanisms 15, 14 of a speed change unit 10 at a plurality of stages of speed reduction ratio. The vehicle runs at a variable speed using the power from the engine 1 while motors 6 and 7 apply a driving torque or regenerative torque to a second output shaft 4s of the first power distributor 4 and a second output shaft 5s of the second power distributor 5, respectively.