PURPOSE: To prevent the clogging of a filter by dropping the dust released in backwashing in the flow direction of exhaust gas so as not te disturb the dust collection and filtration of the exhaust gas, and further providing a thin- film layer on a filter element.

CONSTITUTION: The filter element 1 has a U-shaped section, and made of a porous ceramics, etc., having coarse pores, and the surface of the vertical plate is covered with the thin-film layer 1a hiving micropores. The adjacent elements 1 of the filter 3 are turned to the direction before and behind by an angle of 90° to each other, the elements are laterally assembled in multiple layers, an inlet passage 3a is vertically formed, and an outlet passage 3b is horizontally formed. In addition, an exhaust gas inlet 5 is provided at the upper part of a vessel 4 and a discharge port 9 at the lower part, plural horizontal supporting plates 10 are furnished in the vessel 4, the plural filters 3 respectively supported by the supporting plate 10 are placed on one another so that the inlet passage 3a vertically pierces the filter 3, and a cleaning gas outlet 6 and a backwashing port 7 are provided to each filter chamber 11.