To alleviate an impact applied to an occupant when being transferred from a restriction stage by first tension to a restriction stage by second tension.

The seat belt device is provided with a pre-tensioner control means for primarily restricting the occupant by the first tension by operating a first pre-tensioner when the collision is predicted by a collision prediction means, releasing the first tension when the collision is detected during the primary restriction state by the first tension is continued, and controlling operation timing of the second tension by a second pre-tensioner to transfer from the primary restriction stage by the first tension to the secondary restriction stage by the second tension through a alleviation state of the tension.