An optical device includes: a sealed container having edge walls facing each other in a thickness direction of the container and a side wall connecting both of the edge walls; a first liquid with polarity or electrical conductivity and sealed within the container; a second liquid that is sealed within the container and does not mix with the first liquid; and a voltage applying unit for applying a voltage across the first liquid. The first liquid and the second liquid have equal specific gravity, and transmissivity of the first liquid is lower than the transmissivity of the second liquid. An interface between the first liquid and the second liquid changes shape in response to a voltage applied by the voltage applying unit. A light transmission path that passes through the edge walls and extends in a direction of the thickness of the container is formed.