An optical device includes: a light modulation unit configured to modulate a light according to image information, including an element substrate having a pixel electrode and a switching element connected with the pixel electrode, and an opposed substrate disposed opposed to the element substrate; a frame configured to hold the light modulation unit; and an incident side dustproof glass disposed in close contact with a light incident side end surface of the opposed substrate, the incident side dustproof glass having the plane size larger than the plane size of the opposed substrate is disposed on the light incident side of the frame.