An optical element includes an airtight container having opposing face walls in a thickness direction, and side walls connecting the end face walls; a first liquid sealed in the container and having polarity or conductivity; a second liquid sealed in the container and not mixed with the first liquid so as to define an interface between the first liquid and the second liquid; and voltage applying means for applying a voltage to the first liquid. Further, the first liquid and the second liquid have the same specific gravity and substantially the same refractive index, and minute particles made of a material that does not transmit light are mixed in the first liquid, such that the first liquid has less light transmittance than the second liquid. In a state in which the voltage is applied to the first liquid, the interface between the first liquid and the second liquid deforms, and a transmitting path of light is formed that passes through the end face walls and propagates in the thickness direction of the container.