Provided is an aperture adjusting apparatus for adjusting an aperture through which light transmits. The aperture adjusting apparatus includes: a chamber configured to have space in which fluid flows, the chamber including a lower channel, an upper channel, and a plurality of reservoir regions connecting the lower channel and the upper channel and each having a non-uniform width crossing a flow direction of a fluid to form a space in which fluid flows; a photo-interceptive first fluid and a photo-transmissive second fluid having a property that the photo-transmissive second fluid does not mix with the first fluid and that are prepared in the chamber; and a first electrode unit in which one or more electrodes to which a voltage is applied are arrayed to form an electric field in the chamber, wherein an aperture through which light transmits is adjusted by a location change of an interface between the first fluid and the second fluid according to the electric field.