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.本發明之濃度測定裝置具備：探測器20，其具有對頭部入射測定光之光入射部及檢測傳播於頭部內部之測定光之光檢測部；CPU14，其求取氧化血紅蛋白濃度之隨時間之相對變化量，進行除去該相對變化量所包含之頻率成分中小於特定頻率之頻率成分之濾波處理；及顯示部15，其顯示表示濾波處理後之相對變化量之第1時間序列資料。CPU14判定有無胸骨按壓。於特定時間未進行胸骨按壓之情形時，顯示部15自第1時間序列資料切換顯示表示包含小於特定頻率之頻率成分之相對變化量之第2時間序列資料。
