Image forming method for forming images of plural colors on an image carrier at once

The invention provides an image forming apparatus and an image forming method capable of smoothly and reasonably conducting image formation in case of using a lens (lenses) of which optical magnification is minus. An image forming apparatus of the invention comprises: a line head having lenses of which optical magnification is minus and a light emitter array in which a plurality of light emitting elements are aligned. The lenses are plural in an axial direction (main scanning direction) of an image carrier and a direction (sub scanning direction) perpendicular to the axial direction. A light emitter block composed of "m×n" (in number) light emitting elements is disposed relative to each lens. The "m×n" light emitting elements comprises "n" (in number) light emitting element lines arranged in the direction perpendicular to the axial direction and each light emitting element line includes "m" (in number) light emitting elements aligned in the axial direction. The image forming apparatus further comprises: a control means for actuating the respective light emitting elements to emit lights to be inversed in the axial direction and the direction perpendicular to the axial direction to form an image on the image carrier. In this manner, images of plural colors are formed on the image carrier at once.