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, and a CPU 14 determining temporal relative change amounts of oxygenated hemoglobin concentration and deoxygenated hemoglobin concentration and determining a correlation coefficient of the relative change amounts and a polarity of a slope of a regression line. A concentration measurement apparatus and a concentration measurement method that enable evaluation of the accuracy of calculation and the possibility of reverse direction blood transmission from the vena cava to the head based on the phase shift between the oxygenated hemoglobin concentration and the deoxygenated hemoglobin concentration are thereby realized.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；及CPU14，其求取氧化血紅蛋白濃度及脫氧血紅蛋白濃度之隨時間之相對變化量，求取該等相對變化量之相關係數及回歸直線之斜率之極性。藉此，實現一種可基於氧化血紅蛋白濃度與脫氧血紅蛋白濃度之相位偏差而評估運算之正確性或自大靜脈對頭部反方向供血之可能性之濃度測定裝置及濃度測定方法。
