A living body light measuring device including plural light-radiating devices for radiating light to a head of a subject, plural light-receiving devices for detecting light which is transmitted through the head of the subject after radiation from the light-radiating devices, a calculator for calculating a change of concentration of oxidized and deoxidized hemoglobin in the head of the subject at a measurement point using a pair of each of the plural light-radiating devices and corresponding ones of the light-receiving devices. The calculator decides whether the oxidized hemoglobin concentration change and the deoxidized hemoglobin concentration change are statistically significant at each of the measurement points, and the display displays the decisions regarding the individual measurement points.