In a biophotonic measurement apparatus using a probe having a plurality of irradiation-detector distances (SD distances) in order to separate light absorption changes in a surface layer and a deep layer of a biological tissue on the basis of near infrared spectroscopy, light reception sensitivity is stabilized on each subject/each region by adjusting an attenuation amount of light to be transmitted or received. It has a light source, a detector for detecting light that has been irradiated from the light source to an irradiation point on the subject and propagated in the subject, a light attenuation amount adjusting means to be disposed on an optical path between the light source - the subject or a photodetector - the subject, an analysis unit for analyzing a signal and a display unit for display a result of analysis, the light source and the detector are respectively arranged such the SD distance defined as a distance between an irradiation point and a detection point is given in two or more kinds, the analysis unit analyzes a measurement signal and calculates a light attenuation adjustment amount for setting respective received light amounts within a predetermined range, and the light attenuation amount adjusting means makes attenuation amounts of light respectively adjustable from the result of analysis by changing an amount of light that is incident upon the detector.
