In a clamping device which serves to connect two profile section parts, in particular a horizontal beam (2), to a vertical support (1), an axially movable, spring-loaded retaining pin (7) is located at the end of one profile section part (2). The T-shaped head (8) of the retaining pin (7) engages behind a longitudinal groove (16) of the other profile section part. By means of a screw (12), which is eccentrically supported and engages in a conical recess (10) of the retaining pin (7), the retaining pin is drawn axially inwards in order to fix the two profile section parts (1, 2) to one another. For the purpose of simple assembly and to prevent the retaining pin from jumping out if the screw is rotated in the wrong direction, the retaining pin (7) has a snap-in connection to the insertion core.