A projection type display apparatus includes: an illumination optical system which has a first array lens and a second array lens each of which has a plurality of lens elements having a plurality of rectangular shape openings and arranged in a matrix form; an illumination light source device which has one or more light sources having a polarization degree not smaller than 50% and one or more polarizers for transmitting one type polarized light and reflecting other type polarized light. At least one set of the light sources are arranged so that the polarization directions of light fluxes having high polarization degrees may be perpendicular to each other, the light fluxes are combined by the polarizer, condensed to a single region by a light-flux condensing element, and then directed toward another illumination optical system located in a subsequent stage.