PURPOSE: To restrain the amount of ozone generation and to facilitate the maintenance, such as the washing of electrode, by constituting a discharge electrode of the plate body whose end surface confronting a counter electrode is formed in a curved surface.

CONSTITUTION: Corona discharge is generated between the counter electrode 5 and the discharge electrodes 1 confronting it with required distance and the dust in the air is charged by this corona discharge to be collected. The discharge electrode 1 is constituted of the plate body whose end surface 1a confronting to the counter electrode 5 is formed in a curved surface. As a result, the amount of ozone generation is restrained to the utmost, and the stability in lapse of time having excellent electro-discharge property is obtained. And, the handling in construction, transportation, and maintenance, such as the washing of electrode, are facilitated.