A concentration measurement apparatus includes a probe 20, having a light incidence section making measurement light incident on the head and a light detection section detecting the measurement light that has propagated through the interior of the head, a CPU 14 determining a temporal relative change amount of oxygenated hemoglobin concentration and performing a filtering process of removing frequency components less than a predetermined frequency from frequency components contained in the relative change amount, and a display section 15 displaying first time series data indicating the filtering-processed relative change amount. The CPU 14 judges whether or not chest compression is being performed. If chest compression is not performed for a predetermined time, the display section 15 switches from displaying the first time series data to displaying second time series data indicating the relative change amount that contains frequency components less than the predetermined frequency.
