Abstract: Exposure areas are wholly overlapped by moving a gradient refractive index lens array in a direction perpendicular to a scanning direction, or by providing a plurality of gradient refractive index lens arrays, an optical filter having a density distribution of lightness and darkness to compensate light transmission nonuniformity of the gradient refractive index lens array is arranged, or an opening control plate for limitedly using only of a uniform portion is provided. Two or more means may be simultaneously provided among the aforementioned mean. Moreover, any one of a microscopic transmission shutter array, a microscopic reflection shutter array, and a microscopic light emitter array is used instead of a mask, or an illuminating device and the mask.