A color combining optical system includes a first polarization splitting surface for light in a first wavelength range, and a second polarization splitting surface for light in a second and third wavelength range. The first polarization splitting surface guides illumination light in the first wavelength range to a first liquid crystal display (LCD) element and guides image light reflected from the first LCD element to a direction different from the illumination light. The second polarization splitting surface separates illumination light in the second and third wavelength range from each other, guides them to a second and third LCD element, respectively, and combines image light reflected from the second LCD element with image light reflected from the LCD element to guide combined light to the first polarization splitting surface which combines the image light reflected from the first LCD element with the combined light.