A projection type display apparatus comprising: a liquid crystal display device; a light source portion (1, 2); a first lens array in which a plurality of lens cells are two-dimensionally arranged to receive light emitted from the light source portion (1, 2); a second lens array opposed to the first lens array, having a plurality of lens cells corresponding to said first lens array; a superposition lens located in the region between the second lens array and the liquid crystal display device, adapted to superpose an image of said first lens array on a display surface of the liquid crystal display device, which is adapted to modulate incident light from said superposition lens; and a projection lens adapted to enlarge and project modulation light emitted from the liquid crystal display device; the projection type display apparatus being characterized by: an illumination diaphragm located in the region between the first lens array and the superposition lens in the vicinity of said second lens array and adapted to form a diaphragm aperture in a rectangular shape when it shades the plurality of cells of the second lens array in a linear or straight direction, wherein the sides of the diaphragm aperture of said rectangular shape are parallel to the sides of the lens cells of said second lens array and cells of the liquid crystal display device; and a projection lens diaphragm, located in the projection lens in the vicinity of a pupil of said projection lens and adapted to form a diaphragm aperture in a rhombus shape when it is narrowed, wherein a diagonal line of said rhombus shape is perpendicular or parallel to the sides of the rectangular shape of the illumination diaphragm. a liquid crystal display device; a light source portion (1, 2); a first lens array in which a plurality of lens cells are two-dimensionally arranged to receive light emitted from the light source portion (1, 2); a second lens array opposed to the first lens array, having a plurality of lens cells corresponding to said first lens array; a superposition lens located in the region between the second lens array and the liquid crystal display device, adapted to superpose an image of said first lens array on a display surface of the liquid crystal display device, which is adapted to modulate incident light from said superposition lens; and a projection lens adapted to enlarge and project modulation light emitted from the liquid crystal display device; the projection type display apparatus being characterized by: an illumination diaphragm located in the region between the first lens array and the superposition lens in the vicinity of said second lens array and adapted to form a diaphragm aperture in a rectangular shape when it shades the plurality of cells of the second lens array in a linear or straight direction, wherein the sides of the diaphragm aperture of said rectangular shape are parallel to the sides of the lens cells of said second lens array and cells of the liquid crystal display device; and a projection lens diaphragm, located in the projection lens in the vicinity of a pupil of said projection lens and adapted to form a diaphragm aperture in a rhombus shape when it is narrowed, wherein a diagonal line of said rhombus shape is perpendicular or parallel to the sides of the rectangular shape of the illumination diaphragm. an illumination diaphragm located in the region between the first lens array and the superposition lens in the vicinity of said second lens array and adapted to form a diaphragm aperture in a rectangular shape when it shades the plurality of cells of the second lens array in a linear or straight direction, wherein the sides of the diaphragm aperture of said rectangular shape are parallel to the sides of the lens cells of said second lens array and cells of the liquid crystal display device; and a projection lens diaphragm, located in the projection lens in the vicinity of a pupil of said projection lens and adapted to form a diaphragm aperture in a rhombus shape when it is narrowed, wherein a diagonal line of said rhombus shape is perpendicular or parallel to the sides of the rectangular shape of the illumination diaphragm.