A calibrator according to the present invention is characterized in that calibration of optical characteristics of an optical measurement device (2) in water by inserting a measurement probe (3) connected to an optical measurement device (2) for performing optical measurement on living tissue (Second background calibrator 45) for carrying out calibration, comprising: an accommodating portion (first accommodating portion 451) having an opening at one end and containing water, and the measuring probe (3) is inserted A sealing member (453) which forms a through hole (4532) and seals the opening, a sealing member (453) which seals the opening, and a sealing member (453) which is disposed in water at a position through which the central axis of the through hole (4532) passes, And a removal member (454) for removing adhering substances adhered to the tip of the measurement probe (3) inserted in the measurement probe (3).本発明にかかる校正器は、生体組織に対して光学測定を行う光学測定装置(2)に接続される測定プローブ(3)を挿入して水中における光学測定装置(2)の光学特性の校正を行うための校正器(第2バックグラウンド校正器45)であって、一端に開口部を有し、水を収容する収容部(第1収容部451)と、測定プローブ(3)が挿通される貫通孔(4532)が形成されるとともに、開口部を封止する封止部材(453)と、貫通孔(4532)の中心軸が通過する位置であって水中に配置され、該貫通孔(4532)に挿通された測定プローブ(3)の先端に付着した付着物を除去する除去部材(454)と、を備えた。
