To accurately surface-measure the birefringence of a fine area of a film having a fine structure.

Light from a light source 11 is received by a CCD camera 24 via a collimator 15, a first linear polarizer 16, a first /4 wavelength plate 17, a color filter 100, a second /4 wavelength plate 21, a second linear polarizer 22, and a telecentric lens 23. Rotation of the first /4 wavelength plate 17 by a predetermined angle and imaging by the CCD camera 24 are repeated until the first /4 wavelength plate 17 makes a circuit. Regarding an image imaged by the CCD camera 24, data of luminance variation synchronized with the rotation of the first /4 wavelength plate 17 is acquired for each predetermined pixel by the CCD corresponding to each area of a color filter 100. The birefringence in each area 101 is calculated based on the data of luminance variation.