PURPOSE: To prevent the lowering of dust collecting efficiency by easily removing dust adhered to ionization line without the need for manual works by providing an incineration means in which ionization line is energized at low voltage to incinerate dust adhered to the line.

CONSTITUTION: An incineration means in which the ionization line 4 is energized at low voltage to incinerate dust adhered to the ionization line 4 is provided. For example, dust collection is made by applying DC high-voltage to the ionization line 4 by closing the power switch 9 and also by connecting the alteration switch 13 to the contact a side through the relay circuit 15. When the dust collecting efficiency is lowered by the adhesion of dust to the ionization line 4 during dust collection for long time, the reduction of corona current is detected by the current detector 14 and the relay circuit 15 is operated, whereby the alteration switch 13 is connected to the contact 2 side and the low voltage E1 from the tap 16 of the transformer 10 is applied to the both sides of the ionization line 4. Thus, the adhered dust is incinerated and removed and normal dust collecting activity is again restored by the operation of the relay circuit 15.