PROBLEM TO BE SOLVED: To provide a concentration measurement device and a concentration measurement method capable of evaluating the accuracy of calculation or the possibility of backward blood transmission from the main vein to the head based on a phase shift between an oxygenated hemoglobin concentration and a deoxidized hemoglobin concentration.SOLUTION: The concentration measurement device includes: a probe 20 having a light incident part for making measurement light incident on a head, and a photodetection part for detecting the measurement light having propagated inside the head and a CPU 14 which obtains the temporal relative change amounts of an oxygenated hemoglobin concentration and a deoxidized hemoglobin concentration, and obtains a numerical value representing a phase shift between the relative change amounts.SELECTED DRAWING: Figure 3COPYRIGHT: (C)2017,JPO&INPIT
