PURPOSE: To prevent leak current occurring in the water contents in liquid to be treated and improve safety and economic efficiency by supporting dust collectors and electrodes in a mutually spaced state.

CONSTITUTION: Dust collectors 11 are constituted of platelike insulators, and are disposed between a pair of electrodes 10A and 10B by as much as a required number of plates. In this case, the collectors 11 are disposed in parallel with the electrodes 10 and by maintaining a constant spacing, and are fitted into between the channels 12a, 12b of a pair of supports 12A, 12B in which both end parts of the electrodes 10 and the collectors 11 are oppositely disposed. Accordingly to this device, the resistance between the adjacent electrodes when the water contents in the liquid are sucked by the collectors 11 is only the resistance on both surfaces of the supports 12, and leak current is kept extremely small.