To alleviate a measuring error by correcting one or both of mark and reference waveforms in response to a waveform difference between the mark and the reference waveforms.

One or both values of a mark waveform and a template waveform is corrected at a ratio responsive to positions so that a difference of the mark and the template waveforms becomes a minimum at each template position in a waveform correcting step. For example, one or both values of the mark and the template waveforms is corrected so that the difference of the mark and the template waveforms becomes a function approximated value by function approximating the difference of the mark and the template waveforms at the respective positions by using a least square approximation method or the like for the respective positions by a preset error function. After the correction, likelihood (degree of coincidence) of a center of the mark is repeatedly calculated in a preset mark position measuring range for the corrected mark waveform in a coincidence calculating step, and a change of the degree of the coincidence is calculated.