Abstract: A clamping device for clamping mouldings for a frame assembling machine having a mobile plate (4) that carries a straight sliding clamp (6), returned by a spring and rotary clamp (7), each adapted to engage one of two mouldings to be clamped and assembled. The sliding clamp (6) is fixed to a jib (8) which extends beneath the mobile plate (4). The rotary clamp (7) is integral with a spindle (9) passing through the mobile plate and which bears in its lower part a lever (10) extending towards the jib (8) whereto it is fixed by an anchoring pin (11).