A solid sample used as a reference sample for calibration for calculating the concentration of hemoglobin in living tissue and the oxygen saturation of hemoglobin has a plurality of colorants of non-biological material, and adjusts the mixing ratio of the plurality of colorants Thus, the non-biological material is made of a coloring material group reproducing the light absorption characteristics of hemoglobin having a predetermined concentration and a predetermined oxygen saturation, and a resin material in which each coloring material of the coloring material group is dispersed. In preparation of this solid sample, after preparing a coloring material group reproducing hemoglobin absorption characteristics having a predetermined concentration of hemoglobin and a predetermined hemoglobin oxygen saturation, in a mixed solution in which the coloring material group is dispersed in an organic solvent Dissolve the base resin. Thereafter, the organic solvent is volatilized from the mixed solution in which the resin is dissolved to prepare the solid sample.生体組織のヘモグロビンの濃度及びヘモグロビンの酸素飽和度を算出するためのキャリブレーション用参照試料として用いる固体試料は、非生体物質の複数の色材を有し、複数の色材の混合比率を調整することにより、所定の濃度及び所定の酸素飽和度のヘモグロビンの吸光特性を再現した色材群と、前記色材群の各色材が分散した樹脂材と、を有する非生体物質からなる。この固体試料の作製では、所定のヘモグロビンの濃度及び所定のヘモグロビンの酸素飽和度を有するヘモグロビン吸光特性を再現した色材群を作製した後、前記色材群を有機溶媒に分散させた混合溶液に、母材となる樹脂を溶解させる。この後、前記樹脂の溶解した前記混合溶液から前記有機溶剤を揮発させて前記固体試料を作製する。
