A electrostatic precipitator (ESP) is a means to collect PM. They are characterized by a high total particle collection efficiency with a low pressure drop. The particle behavior in ESP depends on the particle characteristic, electric field, space charge and flow pattern. It is important to understand the particle behavior in ESP. Particle image velocimetry (PIV) was used to grasp the particle behaviour in ESP. In this paper, results of Particle Image Velocimetry (PIV) of the particle flow velocity fields in a wire-to-plate type ESP model are presented. The ESP was an acrylic parallelepiped with a wire-electrode and plate collecting electrode. The positive and negative DC voltages were applied to the wire-electrode, placed at right angles to the main gas flow. The obtained results show that the particle flow velocity increased with increasing discharge current. This is attributed to increase in ionic wind. The particle velocity right under of the wire-electrode was the fastest.