PURPOSE: To obtain an electric precipitator which can be installed in a mobile object and has a good dust collecting effect by a method in which dust contained in air is charged, stuck to the sidewall of a rotary electrode plate when passed between the rotary electrode plate and a fixed electrode plate, and scraped off by a dust removing member to be received in a box.

CONSTITUTION: When a driving motor is actuated, a driving shaft is rotated, and each rotary electrode plate 23 is rotated. Each rotary electrode plate 23 passes the current through a positive electrode, and each comb part 22b of a dust removing member 22 is brought into sliding contact with each sidewall 23 of them. Besides, each fixed electrode plate 8 on the side of a frame main body 1 passes the current through a negative electrode. An electric field having Coulomb force is formed between both electrode plates 23, 8. DC high voltage is applied to a discharge member 11, and a discharge part is formed in the inflow port 4 of the frame main body 1. When air containing dust is introduced to the inflow port 4, the dust is charged in the discharge part to be stuck to the sidewall 23a of each rotary electrode plate 23 when it passes between both electrode plates 23, 8. The dust is scraped off by the comb part 22b of the dust removing member 22 to be received in a dust receiving part 33.