An image forming optical element is provided, in which a first lens, a second lens, and a light guiding unit that leads the light input from the first lens, to the second lens, the light guiding unit has a curved shape of a first curve portion and a second curve portion from the first lens to the second lens, a first reflection face that reflects the light input from the first lens, to the second curve portion, is formed on an outer peripheral face of the first curve portion, a second reflection face that reflects the reflected light to the second lens is formed on an outer peripheral face of the second curve portion, the light input to the first lens travels in the transparent medium until reading the second lens, is output from the second lens, and then forms an image at magnification of erection equal-magnification.