1. A perfecting press apparatus, comprising: at least a first image forming unit, a second image forming unit and a third image forming unit; and a charge controlling unit of corona discharging type; wherein each of the first, second and third image forming units includes: an image carrier; a charging unit for evenly charging the image carrier; an exposure unit for making image exposure on the charged image carrier on the basis of image information to thereby form an electrostatic latent image on the image carrier; a developing unit for supplying developer to the image carrier holding electrostatic latent image to thereby form a toner image on the image carrier; and a transfer unit of corona discharging type for transferring the toner image formed on the image carrier to a transfer medium; the image carriers of the first image forming unit, the second image forming unit and the third image forming unit are alternately arranged at both sides of the transfer medium; the charge controlling unit controls charging polarities of the toner images formed on both faces of the transfer medium by the first and second image forming units before the transfer medium is sent to the third image forming unit; an absolute value of current flowing from the charge controlling unit in the direction of the transfer unit is made larger than an absolute value of current flowing from the transfer unit of the third- image forming unit in the direction of the transferring medium.