Provided are devices and methods to minimize drag caused by abrasion powder between clutch plates and to prevent a faulty engagement or release of a dry clutch. A hybrid driving force transmission device is provided, wherein a multi-plate dry clutch is arranged in a sealed space and used for connecting/disconnecting transmission of a driving force is provided with drive plates, driven plates, friction facings, and a housing cover The drive plates are splined to a clutch hub, and have, in the sections thereof that are splined to the clutch hub, vent holes for channeling the air flowing in the axial direction. The driven plates are splined to a clutch drum. The housing cover has an external air intake hole for drawing external air into the sealed space, and an external air discharge hole for discharging the airflow from the sealed space to the outside.