The invention discloses a chamfering device used for a vehicle-mounted navigation display screen. The chamfering device comprises a chamfering device framework; a display screen limiting cabin is arranged in the chamfering device framework; the bottom part of the display screen limiting cabin is provided with a display screen holding plate; a display screen limiting pad is laid on the upper surface of the display screen holding plate; an L-shaped limiting bar is arranged above the display screen limiting cabin; a limiting lead screw is connected above the L-shaped limiting bar; the limiting lead screw penetrates through the top part of the chamfering device framework and is connected with a connecting loop bar; one side of the connecting loop bar is connected with a limiting handle; and alimiting bar fixing rotary knob is arranged at a position, located at the outer side of the limiting lead screw, on the junction of the limiting lead screw and the top part of the chamfering device framework. The chamfering device disclosed by the invention has the beneficial effects of being compact in structure, simple to operate, and convenient to use; the problem that a display screen cannot be limited when being chamfered in the prior art is solved; meanwhile, the chamfering device can automatically reset after chamfering operation, so that both time and labor are saved, the display screen can be conveniently taken out, and defects in the prior art are solved.