Abstract: A novel weighting device for draft rollers, in which a diaphragm is provided, as a pressing unit, above each top side roller. The diaphragms provided on a spinning frame are classified into a plurality of groups corresponding to species of rollers such as front rollers, middle rollers, and back rollers. Each group of diaphragms has common piping having a regulator for air pressure and branched to the diaphragms belonging to the group. One end of the piping is connected to a common high pressure air source, from which air of a uniform pressure controlled by the regulator is supplied to the diaphragms belonging to the group. Since a weighting force onto a top side roller is a function of a air pressure supplied to the diaphragm, it can be changed or diminished at once in a centralized manner by adjusting the regulator. Therefore, troublesome adjustment of individual pressing units is unnecessary.