Provided is a lightweight, compact power transmission device for a hybrid vehicle which permits a simplified construction of a speed changing unit that establishes a plurality of gear shift stages and a reduced size of a motor. The power transmission device is provided with a first speed changing unit which has a first input shaft 3 connected to a power shaft 6 of an internal combustion engine 1 and which establishes a plurality of gear shift stages, and a second speed changing unit which has a second input shaft 4 connected to a power shaft of a motor 2 and which establishes a plurality of gear shift stages which is different from that of the first speed changing unit. The power transmission device is provided with a connecting unit 13 which disconnectably connects the first input shaft 3 and the second input shaft 4.