Abstract: A trouser belt, including a single-piece band with a first and second extremity, a box (1) fixed to the first extremity of the band, a plate (14) mounted so as to slide within the box (1) following the longitudinal direction and able to be linked to the second extremity by way of a buckle pin (12), at least one serration (18) longitudinally formed on the sliding plate (14), at least one tappet (25, 26) assembled in co-operation with the box in a longitudinal direction and including a protruding pin (21, 22), a helical spring (24) mounted so as to push the tappet (25, 26) in a position to lock the pin in the teeth of the serration. The mutual longitudinal movement of the box and the plate is therefore avoided, while pressure applied to the tappet against the pressure applied by the spring frees the pin from the serration to allow for the mutual longitudinal movement. A single coaxial spring (24) is implemented to at least one of said tappet (25, 26).