A machine tool providing a large grinding area includes a tool body, a rotary bracket driven by the tool body and a plurality of grinding portions coupled to the rotary bracket. The tool body includes a driving motor and a spindle driven by the driving motor to spin axially. The rotary bracket is coupled to and driven by the spindle to rotate and includes a plurality of connecting portions equally spaced from each other on the circumference formed by rotation of the rotary bracket. The grinding portions are coupled with the connecting portions and have grinding zones at the same horizontal level and are driven by the rotary bracket to rotate synchronously therewith to jointly form a grinding plane. Thereby a larger grinding area can be achieved through smaller grinding discs.