A projection-type video-image-displaying device comprising: a light source (1, 2) which radiates white light; a light-collecting optical element which collects light from the light source (1, 2) and emits the light, wherein the light-collecting optical element is a light multiple reflecting element in which light is reflected more than once to form a light distribution having even intensity on an emitting surface thereof; a rotary color filter which is disposed near the emitting surface of the light-collecting optical element and has a plurality of types of filters for selectively transmitting or reflecting light of a specific color in a predetermined order from white light which is emitted from the emitting surface of the light-collecting optical element; a light modulation element which has a plurality of pixels and which modulates incident light in accordance with an image signal and performs an image display; an illumination optical element which collects emitted light from the rotary color filter and forms illumination light for projecting the emitted light onto the light modulation element; a projection lens which projects an image formed by the light modulation element; and a control device which controls a rotation of the rotary color filter to synchronize with the image display by the light modulation element, wherein the rotary color filter forms, on a part thereof, a light-emitting surface using light from the emitting surface of the light-collecting optical element, the light modulation element is disposed so as to have a conjugate relationship with the light-emitting surface of the rotary color filter such that the aspect ratio (C'/D') of the light-emitting surface is equal to the aspect ratio (E/F) of the effective light modulation surface of the light modulation element, the optical axis of the light-collecting optical element is orthogonal to the surface of the rotary color filter; and the emitting surface of the light-collecting optical element is disposed so as to be inclined with respect to the surface of the rotary color filter at an angle of 1 to 3 degrees. a light source (1, 2) which radiates white light; a light-collecting optical element which collects light from the light source (1, 2) and emits the light, wherein the light-collecting optical element is a light multiple reflecting element in which light is reflected more than once to form a light distribution having even intensity on an emitting surface thereof; a rotary color filter which is disposed near the emitting surface of the light-collecting optical element and has a plurality of types of filters for selectively transmitting or reflecting light of a specific color in a predetermined order from white light which is emitted from the emitting surface of the light-collecting optical element; a light modulation element which has a plurality of pixels and which modulates incident light in accordance with an image signal and performs an image display; an illumination optical element which collects emitted light from the rotary color filter and forms illumination light for projecting the emitted light onto the light modulation element; a projection lens which projects an image formed by the light modulation element; and a control device which controls a rotation of the rotary color filter to synchronize with the image display by the light modulation element, wherein the rotary color filter forms, on a part thereof, a light-emitting surface using light from the emitting surface of the light-collecting optical element, the light modulation element is disposed so as to have a conjugate relationship with the light-emitting surface of the rotary color filter such that the aspect ratio (C'/D') of the light-emitting surface is equal to the aspect ratio (E/F) of the effective light modulation surface of the light modulation element, the optical axis of the light-collecting optical element is orthogonal to the surface of the rotary color filter; and the emitting surface of the light-collecting optical element is disposed so as to be inclined with respect to the surface of the rotary color filter at an angle of 1 to 3 degrees.