The invention provides a biological photometric device characterized by a method of disposing a light source and a light detector, capable of measuring a distribution of concentrations at different depths and changes in the concentration in the case of measuring and forming an image of the concentration of metabolites in an organ and changes in the concentration. The light sources and light detectors are disposed on the subject so that, in the case of measuring a concentration of metabolites in an organ and changes in the concentration in a shallow portion in the subject by using an about midpoint position between each of the light sources and each of the light detectors as a sampling point, measurement is performed by using a sampling point of a pair of the light source and said light detector which are disposed at a small interval. In the case of measurement in a deep portion in the subject, a sampling point of a pair of the light source and the light detector which are disposed at a large interval is used.