PURPOSE: To easily and simply separate a rock falling into the interval of grizzly bars without interrupting an operation when the rock is held and stuck between grizzly bars under way and is not released by joining one end of a connecting bar to the piston rod of a hydraulic cylinder with a pin around a vertical axis.

CONSTITUTION: In a vibrating feeder 20 fitted with a grizzly where a plurality of pieces of grizzly bars 26 are arranged in parallel toward the advancing direction of supplied rocks, one end of the grizzly bars 26 is supported by pins and both a movable bar 26b freely turnable in the horizontal direction and a fixed bar 26a tightly provided in a movable frame 22 are alternately arranged. Furthermore, a stopper 26c is provided projectingly in the lower end of the movable bar 26b and also a spring box 54 is formed by pinching the stopper 26c and repulsively fitting the compression coil springs 56, 58 in both sides thereof. The respective spring boxes 54 are connected by a connection bar 50. The tip of a piston rod 40a is joined to one end of the connection bar 50 by a pin. A hydraulic cylinder 40 is provided in the outside of the movable frame 22.