A beam diameter varying portion varies a first beam diameter of a measuring beam incident on an optical portion to a second beam diameter larger than the first beam diameter. An adjustment portion adjusts a condensing position of the measuring beam on the optical portion based on intensity information of a return beam from a position of an inspection object with the first beam diameter. The beam diameter is varied from the first to the second beam diameter by the beam diameter varying portion at the position adjusted by the adjustment portion to cause the measuring beam having the second beam diameter to be incident. A condensing position can be adjusted in a relatively short time because the measuring beam small in beam diameter is used, and a combined beam can be acquired with high transverse resolution because the measuring beam large in beam diameter is used.
