A color prism capable of separating incident light into four color beams and synthesizing incident four-color beams, and a projection-type image display apparatus employing the color prism. The color prism includes: first through third triangular prisms each having two boundary surfaces which face the other two triangular prisms, and an outer surface which transmits or reflects incident light according to an incidence angle of the light; and first through third dichroic filters respectively interposed among the first through third triangular prisms and selectively transmits or reflects incident light according to wavelength so as to separate incident light into first through fourth light beams according to wavelength ranges and synthesize incident first through fourth light beams. The projection-type image display apparatus includes: a light source emitting light; a polarization beam splitter to transmit or reflect incident light according to a polarization direction; the color prism; first through fourth image forming devices disposed to face the outer surfaces of the first through third triangular prisms, and selectively modulates incident first through fourth light beams by pixels to form images and reflects the formed images to the color prism; and a projection lens unit to enlarge and project an incident image formed by the first through fourth image forming devices and synthesized by the color prism onto a screen.