In an emergency situation of a vehicle, when an acceleration sensor moves an action lever up to a middle point, a forcing means rotates the action lever in its working direction and a pawl is separated from an action wheel by the rotating force of the action lever. Accordingly, a webbing takeup shaft is driven by the action wheel and an occupant restraining webbing is wound on to the webbing takeup shaft, whereby the occupant restraining webbing is caused to secure an occupant tightly, that is, an occupant restraining performance is enhanced.