PURPOSE: To stabilize dust collection efficiency by almost perfectly removing the dust in a filter by mounting a dust collecting filter in a case main body and providing a rotary shaft equipped with an air jet nozzle in the case main body in a freely rotatable and up-and-down movable manner.

CONSTITUTION: A dust collecting filter 5 is set to the interior of a case main body 3 by the setting member 7 provided to the upper part of the case main body 3. A rotary shaft 11 equipped with an air jet nozzle 15 is provided in the case main body 3 in a freely rotatable and up-and-down movable manner. As a result, the dust in the filter is almost perfectly removed and the filter from which dust is removed is reused in a dust collector to make it possible not only to stabilize dust collection efficiency but also to extend the life of the filter.