To obtain an optical block for liquid crystal projector which is practical and compact.

The optical block comprises three reflection type liquid crystal panels RP-R, RP-G, and RP-B which convert polarized light under external control, 1st polarization beam splitters PBS-R, PBS-G, and PBS-B which limit polarized light components of incident light so that necessary polarized light components are made incident on a reflection type liquid crystal panel, color separating and coupling elements CD1 and CD2 which perform color decoupling for splitting the incident white light by three colors, distributing necessary color wavelength components to respective reflection type liquid crystal panels, and inputting them to the reflection type liquid crystal panels and color coupling for coupling again reflected lights of color components after polarization- modulated corresponding to image information controlled from outside by the reflection type liquid crystal panels, and 2nd polarization beam splitters PBS-R, PBS-G, and PBS-B which separate the polarization-modulated output light to an output direction or a non-output direction according to its polarization; and the colors separating and coupling elements are different elements in terms of optical paths and are arranged spatially adjacently to each other.