A photosensitive member is movable in a first direction. A line head is provided with a plurality of organic-EL photo emitters, arrayed in a second direction perpendicular to the first direction to form a plurality of photo emitter arrays arranged in the first direction. A plurality of imaging lenses are arrayed in the second direction to form at least one lens array, so that an array of pixels defined on the photosensitive member are subjected to multiple exposure to light emitted from the photo emitter arrays in accordance with the movement of the photosensitive member, thereby forming an electrostatic latent image on the photosensitive member. At least one chromatic-aberration correcting lens is adapted to correct chromatic aberration of the imaging lenses relative to the first direction, and disposed between the photo emitter arrays and the lens array.