An apparatus for measuring a semiconductor device includes a beam irradiating unit configured to irradiate a first beam to a semiconductor substrate, a stage configured to receive the semiconductor substrate thereon and which is configured to rotate toward a central axis, which is perpendicular to a horizontal plane lying in the same plane with the semiconductor substrate, by a first angle to the horizontal plane and a second angle that is different from the first angle, a detector configured to receive a second beam generated by reflecting the first beam to the semiconductor substrate at the first angle and to receive a third beam generated by reflecting the first beam to the semiconductor substrate at the second angle, and an arithmetic operation unit configured to generate a 3D image of the semiconductor substrate using the second beam and the third beam received by the detector.