A concentration measurement apparatus includes a probe, 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 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 displaying first time series data indicating the filtering-processed relative change amount. The CPU judges whether or not chest compression is being performed. If chest compression is not performed for a predetermined time, the display section 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.
