Multiple rays such as scattered lights and fluorescent lights emitted radially in a variety of directions from each bright point in a measurement area enter an objective lens, where the multiple rays are converted into a parallel beam. The parallel beam is reflected by both a reference mirror unit and an oblique mirror unit, and the reflected beams pass through an imaging lens to form an interference image on a light-receiving surface of a detection unit. The detection of the light intensity of the interference image on the light-receiving surface enables an acquisition of the interferogram (the waveform of the change of imaging intensity) in which the light intensity continuously changes. By Fourier-converting the interferogram, spectral characteristics can be obtained which show the relative intensities for each wavelength of the lights emitted from one bright point of an object to be measured.
