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.【課題】酸素化ヘモグロビン濃度と脱酸素化ヘモグロビン濃度との位相ずれに基づく、演算の正確性や大静脈から頭部への逆方向送血の可能性を評価することが可能な濃度測定装置および濃度測定方法を提供する。【解決手段】濃度測定装置は、頭部に測定光を入射する光入射部と、頭部の内部を伝搬した測定光を検出する光検出部とを有するプローブ２０と、酸素化ヘモグロビン濃度及び脱酸素化ヘモグロビン濃度の時間的な相対変化量を求め、これら相対変化量の相関係数および回帰直線の傾きの極性を求めるＣＰＵ１４とを備える。【選択図】図３
