A projection-type display device (1;10) comprising: two light sources (21a, 21b) arranged oppositely to each other on a line and arranged so as to emit illumination lights (220a, 220b) in opposed directions from each other; a photosynthetic unit arranged in one intermediate position on said line, the photosynthetic unit being configured to reflect the illumination lights (220a, 220b) emitted from the two light sources (21a, 21b), received on two reflection parts (223a, 223b) in one direction thereby synthesizing and emitting the illumination lights (220a, 220b) to a single light flux; a color separator configured to divide at a color separating surface the single light flux synthesized by the photosynthetic unit, and to emit respective color lights having different wavelengths respectively; a light modulating unit configured to optically modulate the respective color lights divided by the color separator, based on video signals and to emit the respective color lights as modulated lights of respective colors; a color synthesis unit configured to synthesize the modulated lights of respective colors optically modulated by the light modulating unit respectively and to emit the modulated lights as image light; and a light projecting unit configured to project the image light synthesized by the color synthesis unit, in enlargement, wherein the single light flux synthesized by the photosynthetic unit has a cross section shaped so that a length of a first axis along the direction of the line is longer than a length of a second axis along a direction perpendicular to the direction of the first axis, the color separating surface of the color separator is slanted to an optic axis of the single light flux at a predetermined angle, and the color separator is arranged with respect to the two light sources (21a, 2 1 b) so that the slanting direction of its color separating surface extends at a right angle to the projection on the color separating surface of the line on which the two light sources (21a, 21b) are arranged and to the first axis of the single light flux. two light sources (21a, 21b) arranged oppositely to each other on a line and arranged so as to emit illumination lights (220a, 220b) in opposed directions from each other; a photosynthetic unit arranged in one intermediate position on said line, the photosynthetic unit being configured to reflect the illumination lights (220a, 220b) emitted from the two light sources (21a, 21b), received on two reflection parts (223a, 223b) in one direction thereby synthesizing and emitting the illumination lights (220a, 220b) to a single light flux; a color separator configured to divide at a color separating surface the single light flux synthesized by the photosynthetic unit, and to emit respective color lights having different wavelengths respectively; a light modulating unit configured to optically modulate the respective color lights divided by the color separator, based on video signals and to emit the respective color lights as modulated lights of respective colors; a color synthesis unit configured to synthesize the modulated lights of respective colors optically modulated by the light modulating unit respectively and to emit the modulated lights as image light; and a light projecting unit configured to project the image light synthesized by the color synthesis unit, in enlargement, wherein the single light flux synthesized by the photosynthetic unit has a cross section shaped so that a length of a first axis along the direction of the line is longer than a length of a second axis along a direction perpendicular to the direction of the first axis, the color separating surface of the color separator is slanted to an optic axis of the single light flux at a predetermined angle, and the color separator is arranged with respect to the two light sources (21a, 2 1 b) so that the slanting direction of its color separating surface extends at a right angle to the projection on the color separating surface of the line on which the two light sources (21a, 21b) are arranged and to the first axis of the single light flux.