An illuminating unit with a compact design which is capable of improving collimating characteristics of beams emitted from a plurality of light sources positioned at different locations, and a projection-type image display apparatus employing the illuminating unit. The illuminating unit includes a base, a plurality of light sources that are positioned at different locations on the base to emit beams of different wavelength bands, and at least one color filter with a predetermined curvature to reflect one or more beams of predetermined wavelengths from among the beams emitted by the plurality of light sources such that the reflected one or more beams propagate in a first direction and to pass one or more remaining beams of other wavelength bands. In the illuminating unit, the beams of different wavelength bands emitted by the plurality of light sources are combined to emit a combination of these beams in the first direction. The projection-type image display apparatus includes the illuminating unit, an optical integrator to receive a collimated beam from the illuminating unit and to make a uniform therefrom, an image-forming system to receive the uniform beam from the optical integrator and to produce an image by selectively reflecting the uniform beam, a beam splitter disposed in an optical path between the illuminating unit and the image-forming system to change the optical path of incident beams such that a beam incident from the illuminating unit is directed toward the image-forming system while a beam incident from the image-forming system is directed toward a screen, and a projection lens unit disposed adjacent to the beam splitter opposite the image-forming system to enlarge the image produced by the image-forming system and to project the enlarged image onto the screen.