PURPOSE: To release the powder such as nonburned carbon incorporated in an exhaust gas from a small body of a grain layer efficiently by causing the corona discharge between a corona discharge electrode and a corresponding electrode and transferring the small body along the corresponding electrode.

CONSTITUTION: The small bodies 16 adhered with the electrically-conductive powder 15 are allowed to fall down continuously on an electrically-conductive mesh 14 and transferred to the lower direction along the mesh 14. At this time, the corona discharge is caused between a discharge electrode 13 and the mesh 14. Therefore while the small bodies 16 fall from the lower end of the mesh 14 to the base part of a vessel 12, the powder 15 stuck on the surface of the small bodies 16 is peeled from the small bodies 16. The small bodies 16 removed with the powder 15 fall from the lower end of the mesh 14 and are collected in a space compared with a partition plate 18. In such a way, the power removal is efficiently performed in a small size by inexpensive means.