The vehicle seat of a vehicle has a seat carrier with a side part, a buckle of a safety belt positioned thereon and a vertically adjustable underframe. The underframe is provided with a sector. An engaging element is arranged on the seat carrier and is designed to cooperate with the sector gear. During normal, non-accidental circumstances of the vehicle the sector gear is in a position of rest in which the engaging element is free from the sector gear. The buckle is connected to an upper end of a means with tensile strength that is connected to cooperate with the engaging element. In an accident situation the engaging element engages the sector gear. There is provided a tightening unit for the belt that has a driving cylinder. The means with tensile strength is deflected in its direction at a point of deflection. A lower portion of the means with tensile strength runs substantially in longitudinal direction of the side part. The other end of the means with tensile strength is arranged on the driving cylinder. A holding means for the tightening unit is provided on the side part.