An apparatus for detecting a position of a target mark out of a plurality of marks in a region of an object to obtain a position of the region of the object. The apparatus includes a scope configured to sense a first image of the object at a first magnification and a second image of the object at a second magnification higher than the first magnification, and a processor configured to extract, from the first image, a position of a first mark out of the plurality of marks and a feature of a region outside the first mark, to identify the first mark based on the extracted feature, to extract, from the second image, a position of the target mark, to evaluate reliability of the extracted position of the target mark, to select a second mark, different from the target mark, from the plurality of marks as a new target mark based on the evaluated reliability and the identified first mark in order to extract a position of the selected second mark from an image sensed by the scope at the second magnification.