Abstract: A machine for shredding a discarded tire is composed of a base, a vertical advancing seat, a horizontal advancing seat, a tire holding device, a transmission device, a tool set, and a computer control device. The vertical advancing seat is provided with a slide block capable of sliding along the vertical advancing seat in the vertical direction relative to the base. The horizontal advancing seat is mounted on the slide block of the vertical advancing seat and is provided with a slide block capable of sliding along the horizontal advancing seat in the horizontal direction relative to the base. The horizontal advancing seat is further provided with two sensors, whereas the slide block of the horizontal advancing seat is provided with two sensing blocks capable of cooperating with the sensors to execute the step-by-step shredding operation is conjunction with the tool set and the computer control device.