A power transmission device is provided, which includes a vibration reducing damper provided on a power transmission path, and a clutch mechanism having a plurality of friction plates, a hydraulic pressure chamber, and a centrifugal balance chamber provided opposed to the hydraulic pressure chamber. The clutch mechanism is provided adjacent to an axial side part of the damper, and an oil drain port for hydraulic fluid supplied to the centrifugal balance chamber of the clutch mechanism is provided at a location radially inward of the damper and axially overlapping with the damper.