Disclosed are an electric dust collector apparatus in an electrostatic precipitator system and a method for electrostatic precipitation thereby. The electric dust collector apparatus includes a flow liquid dust collector part collecting charged dust in a liquid flowing to its one side surface, and a counter unit located opposite to the flow liquid dust collector part and including a metal plate charged with the same polarity with the charged dust to guide the induced charged dust to flow toward the flow liquid dust collector part, wherein the counter unit further includes a coating including an insulating material coating the metal plate.