An aperture adjusting apparatus is provided. The aperture adjusting apparatus includes: a variable part of which an aperture size varies; an optical sensor configured to sense light incident to the variable device part and light output from the variable device part; an aperture calculator configured to calculate a size of an aperture formed in the variable part from light intensity sensed by the optical sensor; and a driving controller configured to control driving of the variable device part by receiving a calculation result fed back from the aperture calculator.