The apparatus includes a holder holding an optical element, a back plate supporting the optical element via the holder, a mechanism moving the optical element in a six-degree-of-freedom, a base plate supporting the back plate via the mechanism, and six displacement sensors disposed on the base plate and measuring displacement amounts of different points on the optical element. The displacement sensors includes three ones measuring them in a first direction, one measuring it in a second direction, and two ones measuring them in a third direction. The apparatus further includes a transformation processor transforming the six measured displacement amounts into displacement amounts of the optical element in the six-degree-of-freedom, a calibration processor calibrating the transformed displacement amounts, and a controller outputting command values to the displacing mechanism based on differences between the calibrated displacement amounts and target displacement amounts of the optical element.