Abstract: A wet electrostatic precipitator includes an electric field forming unit including a first electrode and a second electrode which form an alternating electric field. The first electrode is a flat plate, and has a plurality of discharge electrodes on a surface that opposes the second electrode. The second electrode includes a discharge frame, a first flat plate portion and a second flat plate portion. The first flat plate portion opposes the discharge electrode of the first electrode. A plurality of discharge electrodes are formed on a surface of the second flat plate portion that opposes the first electrode. The discharge electrodes alternately generate corona discharges having opposite polarities in a direction perpendicular to a flow direction of gas, and alternately apply charges having opposite polarities to mist and dust. The first electrode and the first flat plate portion trap the charged mist and the dust.