The invention discloses a folding protective sleeve for a numerical control cutter and belongs to the field of machining auxiliary equipment. The folding protective sleeve includes a first sleeve plate, placing plates and fixing rings. The first sleeve plate is connected with a second sleeve plate through a second connector, the placing plates are connected with a first connector, and the placingplates are provided with the fixing rings and bearing rings. The placing plates are all provided with the fixing rings and the bearing rings, the fixing rings are arranged at the upper end and used for fixing the upper ends of cutters, the middle portions of the fixing rings are through, to enable the cutters to penetrate the fixing rings conveniently, the bearing rings are arranged at the bottom,and the bottoms of the bearing rings are sealed, to limit one end of each cutter. The placing plates are unequally arranged, to be suitable for cutters of different sizes. The placing plates on the first sleeve plate and the second sleeve plate are staggered. When the first sleeve plate and the second sleeve plate are reeled, the cutters of different sizes and types are staggered, so that the space utilization rate is improved, and a fixing effect of the protective sleeve is enhanced.