A dust collection device for a sanding machine includes a casing located at the lower end of the upright sanding belt and the casing includes a bottom hole which communicates with the open top of the dust collection part. The dust collection part communicates with an exterior collection area defined within an outer cover. A fan unit an a separation plate are located within the outer cover, so that dust during operation of the sanding belt can be collected into the exterior collection area and brought out via an escape pipe connected to the outer cover. A sanding wheel is located beside the separation plate and a housing is mounted to the sanding wheel. The housing includes a restriction plate so as to guide dust during operation of the sanding wheel into the escape pipe. The sanding belt, the fan unit and the sanding wheel share a common axle.