An optical device, includes: an optical modulator that modulates a light beam irradiated by a light source in accordance with image information to form an optical image; an optical modulator holder that has a cooling chamber with cooling fluid sealed therein and holds the optical modulator so that heat can be transferred to the cooling fluid in the cooling chamber; a plurality of fluid circulators communicating with the cooling chamber to guide the cooling fluid to the outside of the cooling chamber and again introduces the cooling fluid into the cooling chamber; a cooling fluid accumulator arranged in a flow path of the cooling fluid in each of the plurality of fluid circulators and having a cooling fluid inflow section that flows the cooling fluid to the inside of the cooling accumulator and a cooling fluid outflow section that flows the cooling fluid to the outside of the cooling accumulator so as to accumulate the cooling fluid in the cooling fluid accumulator; and a fluid press-feeder disposed in the flow path of the cooling fluid in each of the plurality of fluid circulators so that the cooling fluid is forcedly circulated via the plurality of fluid circulators, in which the cooling fluid accumulator includes therein: a bubble trapping having a plurality of holes to circulate the cooling fluid toward the cooling fluid outflow section and trap air bubbles contained in the cooling fluid; and a bubble accumulator that accumulates the air bubbles trapped by the bubble trapping.