To arrange a motor-generator and a start clutch in a compact manner between an engine and a transmission so as to reduce a weight, a dimension, and the number of parts of a dual mass flywheel.

A power transmission device for a hybrid vehicle is provided with the motor-generator MG arranged in series between a crank shaft 11 of the engine E and a main shaft 12 of the transmission T and the start clutch C composed of a wet multiple disk clutch. The start clutch C is stored inside a rotor 14 of the motor-generator MG so that it is substantially stored within a width in the axial direction of the rotor 14. Primary inertia mass composed of the rotor 14 of the motor-generator MG and secondary inertia mass composed of a clutch case 28 of the start clutch C are mutually connected by a damper 13 to constitute the dual mass flywheel FW.