A microscope includes an optical element provided with an anti-reflection film applied thereto. The anti-reflection film has the following layered structure: having first to sixth layers of films, in order from the surface of the optical element, formed of a high-refractive-index material for each of the first, third and fifth layers, a low-refractive-index material or a middle-refractive-index material for each of the second and fourth layers, and a low-refractive-index material for the sixth layer, with a range of the optical film-thickness nd of each layer in reference to the design wavelength λ being “(0.13˜0.35)×λ/4” for the first layer, “(0.18˜0.75)×λ/4” for the second layer, “(0.28˜2.31)×λ/4” for the third layer, “(0.26˜0.92)×60 /4” for the fourth layer, “(0.20˜0.37)×λ/4” for the fifth layer, and “(1.09˜1.18)×λ/4” for the sixth layer.