The inventor provides a fiber cutting device which comprises a cutter roller, a pressing roller, a rubber roller, a pressing support, a pressing mechanism and a power mechanism, wherein the pressing mechanism drives the pressing support to move close to or away from the rubber roller, the power mechanism is in transmission connection with a driving roller to drive the driving roller to rotate, when the pressing support driven by the pressing mechanism is close to the rubber roller, the driving roller driven by the power mechanism drives a driven roller to rotate by friction force, and a short fiber outlet is formed below a device shell or a device outer frame, and is located below the gap between the cutter roller and the rubber roller. In the fiber reinforced composite material mixing equipment, the distance between the fiber cutting device and a feeding port of a second-stage extrusion device is shortened as far as possible, the short fiber cut by the cutter roller directly falls to the feeding port of the second-stage extrusion device as soon as possible, the cluster falling of the short fiber is avoided, and the raw material feeding uniformity of the second-stage extrusion device is improved.