1. An image forming apparatus comprising: means for converting an original image into an electrostatic charge and for maintaining the electrostatic charge; first forming means for forming a first electrostatic latent image on a recording medium according to the electrostatic charge maintained by said converting means; and second forming means for forming a second electrostatic latent image on said recording medium according to an input image signal wherein, in response to a demand for latent image formation by said second forming means during the latent image formation by said first forming means, the function of said first forming means is interrupted and said second forming means is activated, and, the latent image formation by said first forming means, which is performed according to the electrostatic charge maintained by said converting means before the interruption, is started again after the completion of the function of said second forming means.