Interference measurement device and measurement method

[Problem to be Solved] To improve the measurement accuracy of an interference measurement device which utilizes interference of light. [Means for Solution] An interference measurement device includes a light source 10 for emitting supercontinuum light (SC light), an optical fiber coupler 11 for splitting the SC light into measurement light and reference light, a dispersion compensation element 12, a drive unit 13 for moving the dispersion compensation element 12, and light-receiving means 14 for measuring an interference waveform produced as a result of interference between the measurement light and the reference light. A measurement object 15 to be measured is an Si substrate having a thickness of 800 μm. The dispersion compensation element 12 is an Si substrate having a thickness of 780 μm. Namely, the dispersion compensation element 12 is formed of the same material as that of the measurement object 15 and is 20 μm thinner than the measurement object 15. The interference caused by reflection on the back surface of the measurement object 15 and reflection on the back surface of the dispersion compensation element 12 has a narrow peak width because wavelength dispersion is cancelled almost completely. Thus, the accuracy in measuring the peak position improves. As a result, the accuracy in measuring temperature, etc., improves.