At the 1st 3 dimensional frame of reference which designates specified position as origin the FBG sensor section on the basis of the detection result of 3 which the FBG sensor section 3A which distribution facilities it does in the interposition section 12 interposing inside suffering inspection person 11 and detects the deformation of interposition section 12 multiple is provided and FBG sensor section 3, frame of reference configuration section 9D and each one which configurate 2nd 3 dimensional frame of reference on the basis of the 1st 3 dimensional coordinate of coordinate calculation section 9C and the respective FBG sensor section 3 which calculate the 1st 3 dimensional coordinate of the respective FBG sensor section 3,The form calculation means 9F which calculate the form of interposition section 12 on the basis of the 2nd 3 dimensional coordinate which is converted by coordinate converter 9E and the coordinate converter 9E which are converted to the 2nd 3 dimensional coordinate in the 2nd 3 dimensional frame of reference which is configurated 1st 3 dimensional coordinate of FBG sensor section 3, by frame of reference configuration section 9D, and, it possesses.被検者11の内部に挿入する挿入部12に配設し挿入部12の歪みを検出するFBGセンサ部3Aを複数設けたFBGセンサ部3と、FBGセンサ部3の検出結果に基づき、所定の位置を原点とする第1の3次元座標系にて、それぞれのFBGセンサ部3の第1の3次元座標を算出する座標算出部9Cと、それぞれのFBGセンサ部3の第1の3次元座標を基に、第2の3次元座標系を設定する座標系設定部9Dと、それぞれのFBGセンサ部3の第1の3次元座標を、座標系設定部9Dにより設定された第2の3次元座標系における第2の3次元座標に変換する座標変換部9Eと、座標変換部9Eにより変換された第2の3次元座標に基づき、挿入部12の形状を算出する形状算出手段9Fと、を有する。
