A dust-proof machine tool which has a handgrip with an aperture to hold a driving switch movable up and down and a control bar hinged thereon to generate a pivotable stroke to press the driving switch. The handgrip is coupled with a dust-proof cover which has an opening to couple on the driving switch and a press portion formed on the perimeter of the opening to press the handgrip and seal the aperture. Thereby during operation of the machine tool, dust can be prevented from entering the machine tool through the driving switch and the aperture to maintain steady operation of the machine tool and enhance the lifespan thereof.