An illumination apparatus includes an illumination optical system configured to illuminate a light modulation element; a plurality of light source units each including a fluorescent member, at least one light source, and a light-guiding optical system; and an optical-path combining system. A predetermined region in an area where light source images are formed by the illumination optical system using light beams from the optical-path combining system is defined as an effective region, and the number of the light source units is denoted by N. In this case, the light source images and N subregions obtained by dividing the effective region by N along a first side direction of the effective region or a second side direction orthogonal to the first side direction satisfy a predetermined relation.