a method of measuring solder bumps formed on a substrate mounting a semiconductor element thereon includes mounting a work to be measured on a work position mechanism , and scanning the work by an optical micro head to measure errors of a mount posture of the work . each stage is controlled to correct the errors , and thereafter , the apex positions of the bumps are scanned and measured . the measurement results are collected by a personal computer , and the measurement results together with control data of each axis are sent to a main personal computer and displayed on its screen . an error of an apex position of each bump from a regression plane is calculated , and if the error is smaller than a reference value , the work is judged to be satisfactory .