PROBLEM TO BE SOLVED: To provide a concentration determination apparatus, a concentration determination method, and a program which highly accurately calculates the concentration of a target component in any layer of an observed object.SOLUTION: A concentration determination apparatus 100 for determining the concentration of a target component in an arbitrary layer of an observed object constituted of a plurality of layers, includes: an optical path length distribution storage unit 102； a time-resolved waveform storage unit 103； an irradiation unit 104 for irradiating, with short time pulse light, the observed object adjusted so that the absorption state of a surface has a prescribed absorption state； a light receiving unit 105 for receiving light in which the short time pulse light is backscattered by the observed object and which is emitted from the surface of the observed object whose absorption state is adjusted； an absorption coefficient calculation unit 110； and a concentration calculation unit 113.【課題】観測対象の任意の層における目的成分の濃度を高精度に算出することが可能な濃度定量装置、濃度定量方法及びプログラムを提供する。【解決手段】複数の層により構成される観測対象のうち、任意の層における目的成分の濃度を定量する濃度定量装置１００であって、光路長分布記憶部１０２と、時間分解波形記憶部１０３と、表面の吸収状態が所定の吸収状態になるように調整された観測対象に短時間パルス光を照射する照射部１０４と、短時間パルス光が観測対象によって後方散乱され、吸収状態が調整された観測対象の表面から射出された光を受光する受光部１０５と、吸収係数算出部１１０と、濃度算出部１１３と、を含む。【選択図】図１
