In an image input device including a multistage aperture (13) which reduces a quantity of light by changing an aperture, and an ND filter (15) which reduces a quantity of light by changing transmittance of passing light, if ghosts tend to occur due to the second light reducing means, the generation of ghosts is effectively avoided. An object determining unit determines whether a strong light source is present on an object image formed by an optical unit (10) for imaging based on luminance distribution on the object image. The multistage aperture (13) and the ND filter (15) are controlled in order to obtain a proper exposure to pickup the object image. If the object determining unit determines which a strong light source is present on the object image, the ND filter (15), which reduces the quantity of light by changing the transmittance of passing light, is used as less as possible, and the multistage aperture (13) is functioned preferentially.