The conditioner for agricultural harvesting machines, in particular for rotary mowers, comprises a substantially cylindrical hollow shaft, which extends transversely to the longitudinal axis of the machine and which - when seen in the direction of movement of the machine - is arranged behind the mowing discs, said hollow shaft having secured thereto a plurality of V-shaped pairs of fingers extending radially outwards. The surface of the hollow shaft is provided with a plurality of spaced, peripheral, outwardly projecting hollow ribs, which extend parallel to the longitudinal axis of the hollow shaft and substantially throughout the whole length of said hollow shaft, whereas each V-shaped pair of fingers is fixedly connected to a supporting base, the longitudinal axis of which extends in the connection direction of the two fingers and the underside of which has a shape adapted to the hollow rib and to the surface of the hollow shaft.