PROBLEM TO BE SOLVED: To appropriately determine a light irradiation position and a light-receiving position according to the depth of a blood vessel from a skin surface in a measurement of a noninvasive blood component measurement.SOLUTION: A tentative measurement light-emitting element 52S' to become an illumination position of measurement light is selected at a same or substantially same (W±&alpha；) position as a distance W, and a tentative measurement light-receiving element 52m' to become a light-receiving position, and a tentative reference light-receiving element 54r' are selected along the orthogonal direction of a center line L, while gradually adding and spreading the distance W from a blood vessel site 7b subject to a measurement to an upper limit value. The tentative measurement light-emitting element 52S' is made to emit light. A transmittance as a ratio of photometric luminance at the tentative measurement light-receiving element 52m' to photometric luminance at the tentative reference light-receiving element 54r' is calculated as an index of the blood vessel depth D of the blood vessel site from the skin surface. A light-emitting element and a light-receiving element selected corresponding to the distance W as a minimum transmittance are determined as the light-emitting element and the light-receiving element for use in the measurement.【課題】非侵襲式の血液成分の測定において、光の照射位置と受光位置とを、皮膚面からの血管の深度に応じて適切に定めることを可能とすること。【解決手段】測定対象の血管部位７ｂから、距離Ｗを徐々に上限値に至るまで加算し広げつつ、中心線Ｌの直交方向に沿って、距離Ｗと同じまたは略同じ（Ｗ±α）位置に、測定光の照射位置となる仮測定用発光素子５２ｓ’と、受光位置となる仮測定用受光素子５２ｍ’と、仮リファレンス用受光素子５４ｒ’とを選択する。そして、仮測定用発光素子５２ｓ’を発光させ、仮測定用受光素子５２ｍ’での測光輝度と仮リファレンス用受光素子５４ｒ’での測光輝度との比である透過率を、当該血管部位の皮膚表面からの血管深度Ｄの指標として算出する。最小透過率となる距離Ｗに対応して選択された発光素子及び受光素子を、測定時に使用する発光素子及び受光素子として確定する。【選択図】図１０
