A projection type image display apparatus comprising a light source, an optical integrator, by which light outgoing from the light source is changed in distribution of illumination, a color separation optical system, by which light outgoing from the optical integrator is separated into a plurality of light beams, and a relay optical system including a plurality of relay lenses, by which light beams separated by the color separation optical system are relayed, and a reflection mirror. The relay optical system includes a device that adjusts angles of inclination of at least one of the relay lenses with respect to an optical axis of illumination of light outgoing from the light source.