Abstract: A soft-focus optical element has a light-transmitting surface formed with a plurality of low refractive index portions each in the form of a lens-like curved surface; the size of each low refractive-index portion is within the following range;0.05 mm.ltoreq..phi..ltoreq.0.5 mm (1)and0.5.mu..ltoreq.h.ltoreq.3.mu. (2)where the diameter of the aperture of the low refractive-index portion is represented by .phi. and the height or depth between the light-transmitting surface and the top of the lens-shaped curved portion of the low refractive-index portion is presented by h; and the ratio S of the area of the plurality of low refractive-index portions to the area of the light-transmitting surface is defined as follows:5%.ltoreq.S.ltoreq.35% (3)The soft-focus optical element may be attached on an image-focusing lens.