An apparatus having image forming units to form respective toner images of different colors on a toner-image receiving medium, each unit including an image carrier, a static-latent-image forming portion to form a static latent image on the image carrier, a developing portion to apply a toner of the corresponding color to the image carrier, for forming the toner image on the image carrier, and a toner transferring portion to transfer the toner image from the image carrier to the medium, wherein the image forming units are disposed so as to be opposed to the medium and operable to sequentially transfer the toner images from the image carriers to the medium, and the developing portion of each unit is operable to adsorb the toner remaining on the image carrier after the toner image is transferred to the medium, and wherein at least the image forming unit located at the most upstream position of the apparatus is provided with a dust removing portion to remove, from the image carrier, a dust which has been transferred to the image carrier during a transfer of the toner image from the image carrier to the medium.