A grid wire cleaning mechanism is provided to prevent a reduction in image quality due to the surface of the electrostatic latent image carrier not being uniformly charged as a result of corona products adhering unevenly to the surface of the grid wires to extend the life of the grid wires and grid wire contact member. A first abrading member 71 abrades grid wires 224. A movement device 73 moves the first abrading member 71 in the same direction as the direction of extension of the grid wires 224. A humidity measurement unit 741 measures the humidity near the grid wires 224. The operation control unit 743 operates the movement device 73 when cleaning the grid wires 224, but does not operate the movement device 73 when the humidity measured by the humidity measurement unit 741 exceeds a predetermined threshold value.