An optical apparatus includes a light quantity adjusting member arranged to vary a quantity of light when the member is moved, a stepping motor arranged to drive the light quantity adjusting member, a luminance detecting part for detecting the luminance of a shooting object on the basis of the quantity of light obtained through the light quantity adjusting member, and a control circuit for driving and controlling the stepping motor in such a way as to make a difference between the luminance of the object detected by the luminance detecting part and a target luminance value smaller, the control circuit being arranged to change the driving speed of the stepping motor to be lowered when the object luminance comes near to the target luminance value.