A dynamic change detecting apparatus permits selection of a combination condition of various detection sensitivities and dynamic ranges. This apparatus has a light source 30 or 100 for emitting light having at least one wavelength component; a detecting element having a detecting part 1 composed by connecting a resonant part 5 including a medium 17 having a predetermined thickness and a total reflection mirror 19 to one end of a transmission/reflection part 3 having transmission/reflection properties varying with a wavelength of incident light, the light emitted by the light source 30 or 100 being entered from the other end of the transmission/reflection part 3 into the detecting element; a plurality of light detectors 91, 92 and 93 for detecting the light reflected by the detecting part 1 to detect a detection signal; and a signal processing unit 97 for detecting dynamic change propagating to the total reflection mirror 19 on the basis of change in amplitude of the detection signal corresponding to change in size of the detecting part 1 caused by propagation of the dynamic change.
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