PURPOSE: To maintain initial characteristics in ordinary operation, and to enhance efficiency, by constituting discharge electrodes only of pieces of wires protruding in the direction opposite to gas flow.

CONSTITUTION: Needle-like pieces 5aW5e protrude from one side of each support pillar 2aW2e only in the direction opposite to gas flow A. Application of high DC voltage between discharging negative electrodes consisting of the pieces 5aW 5e and dust collecting electrodes 1a, 1b causes corona discharge between the tips of the pieces 5aW5e and the electrodes 1a, 1b, and collects dust contained in a gas flowing in the direction A on the dust collecting electrodes 1a, 1b.