The utility model relates to a milling groove processing device used for the input shaft of a redirector. The milling groove processing device comprises a clamping device for an input shaft, and a processing cutter; the clamping device comprises central hole limiting devices arranged at the two ends of the input shaft, and a spring housing clamping oil seal excircle arranged on the outer side of the input shaft; and the processing cutter is a screw-type hob cutter and is perpendicular to the axial direction of the input shaft. In the utility model, two end central hole limitation and spring housing clamping are adopted, through continuous and gradual cutting of the hob cutter and the input shaft, on one hand, the positioning and clamping way is improved, graduation errors during the rotation of the input shaft are reduced, the halving accuracy of six grooves is improved, and on the other hand, the processing way is improved, through the meshed type cutting of the hob cutter and the input shaft according to a certain rotational speed matching relation, the processing time is reduced, and the production efficiency of the input shaft is improved.