To realize a projection image display apparatus using an optical part which can be miniaturized and has sufficient heat resistance instead of a fly-eye lens molded of resin as a lens array generating illuminating light for effectively irradiating an image forming means.

A plurality of distributed refractive index glass arrays 103 worked to a shape similar to the shape of the effective area of the image forming means 105, for example a rectangular shape, are used as the lens array part on which light from a reflector 101 is made incident. The shape of the reflector 101 is made paraboloidal or ellipsoidal shape, and the focal position of gradient index glass material 103a having a previously set refractive index distribution is set at the position of the light emitting surface of the material 103a. The material 103a is adhered or welded with heat resistant adhesive so as to be formed in an array state. A splitting means for splitting light to polarized light beams having the plane of polarization different from each other and a conversion means for converting it by optically rotating the plane of polarization of one split polarized light beam are arranged on both sides of the glass array 103.