A seatbelt retractor for a seat belt device in a vehicle. The retractor includes a frame and a spool configured to be fixed to one end of a seat belt webbing so that the webbing may be wound around the spool. The spool is rotatably mounted at both ends to the frame and configured to rotate in a webbing extraction direction and a webbing retraction direction. The retractor includes primary and secondary torsion bars positioned end to end in the spool along an axis of rotation of the spool. The primary and secondary torsion bars are configured to be locked at second ends of the torsion bars opposite to the first end. The first ends of the torsion bars are configured to rotate relative to the second ends so that the primary and secondary torsion bars deform to absorb force when a vehicle acceleration exceeds a predetermined value.