An illumination device includes: a light source; a polarization converter (114) that converts a light beam irradiated by the light source into a substantially uniform linear polarized light, the polarization converter (114) being slanted relative to a central axis of the light beam irradiated by the light source and including a plurality of polarization-separating films (1141) and a plurality of light reflection films (1143) alternately arranged in a direction substantially orthogonal to the central axis of the light beam irradiated by the light source; an optical filter (311) provided between the light source and the polarization converter (114) and having a plurality of optical conversion layers, which are formed striped with the pitch thereof corresponding to the arrangement of the polarization-separating films (1141) to optically convert the incident light beam; a holder frame (312) that holds the optical filter (311); and a filter-driving mechanism (313) that moves the holder frame (312) in a direction in which the polarization-separating films (1141) are arranged.