PURPOSE: To provide a belt pretensioner of a safety belt having a return brake for reducing a peak of an energy applied to a web when automobile is collided.

CONSTITUTION: The belt pretensioner in a restraining apparatus for vehicle occupants comprises a reel 54 having a slot 58 for passing a web 16 and teeth 56 on the outer periphery. The reel 54 is arranged loosely between teeth arranged opposite spaced apart from each other on two opposing paced part parallel plates 20d, 40. One of the plates forms a drive plate 40 which is displaceable along a bottom wall 20c of a frame 20 to which the other plate 20d is secured as cover plate. A return brake for diminishing energy peaks in the web is formed by a torsion bar 32 on which a gear 34 is mounted via an overrunning clutch 36. The gear 34 is engaged with a teeth 46 of the plate 40. A linear drive engages the plate 40 for moving the plate 40.