The powder image on electrofax paper is inclined to have a striped pattern. This phenomenon is based on the irregularity of the charge density generated from corona discharge around the wire electrode. To research it in detail, electrostatic charge patterns are observed on a single wire electrode fixed over the electrofax paper with or without a semicylindrical shield cover. Then, it became clear that the bands of weak charge density come out at right angles to the wire electrode and under constant points of the wire. Therefore, the direction of the wire electrode was made not at right angles to the directionof scanning motion. The uniformity of the charge distribution improved remarkably.