To provide a measuring method which enables accurate grasp of the shape of a recess.

The method comprises a process (processing S1) for measuring the angle of a lateral wall to the bottom of the recess formed in an insulating film, a process (processing S2) for setting a plurality of parameter groups, inclusive of the angle of the lateral wall to the bottom of the recess, the width dimension and the depth dimension thereof, and preparing a library having a plurality of waveforms of reflected light correlated respectively with the parameter groups, a process (processing S4) for shedding light on the recess, a process (processing S5) for detecting reflected light, a process (processing S6) for collating the waveform of the reflected light with the waveform selected from the library, and a process for setting, as an optimal value, the parameter such as the width dimension of the recess correlated with the selected waveform in the case when discrepancy between the waveform of the reflected light and that selected from the library is less than a prescribed value, and grasping the shape of the recess. The angle of the lateral wall to the bottom of the recess in the parameter groups of the library is a measured value in the processing S1.