A power transmission device that includes an uppermost side bearing; a lower side bearing; an uppermost side lubricating medium storage portion defined between the uppermost side bearing and the case to guide a lubricating medium to the uppermost side bearing; a lower side lubricating medium storage portion defined between the lower side bearing and the case to guide a lubricating medium to the lower side bearing, and located below the uppermost side lubricating medium storage portion when installing the power transmission device for a vehicle on the vehicle; and a communicating passage formed in the case to communicate the uppermost side lubricating medium storage portion and the lower side lubricating medium storage portion with each other.