To eliminate the maintenance of sweeping dust attached to or accumulated in a machine tool body by performing a sufficient operation for filtering ambient air to be sucked into the machine tool.

A filtering device 40 filters out dust or the like caused by ambient air sucked into the machine tool body by a driving motor included in the mounted machine tool body. Here, a circumferential surface (circumferential surface 431 of a cylindrical air sucking section 43) of a housing 41 of the filtering device is provided with an air sucking section 45 of the filtering device 40 to act as a section for sucking ambient air into a centrifugal separation chamber 55. The air sucking section 45 is formed in such a manner that, when the suction air to be sucked into the machine tool body stops to cause the centrifugal separation function of the centrifugal separation chamber 55 to be de-actuated, separated substances D (dust or the like) separated inside the centrifugal separation chamber 55 is discharged through the air sucking section 45 to the outside by the own weight of the separated substance D.