PROBLEM TO BE SOLVED: To accurately detect a horizontal iris position of an object person.SOLUTION: An iris position detection device (1) comprises a gradation processing unit (13) for generating a reference image, a brightness value data generation unit (brightness value graph generation unit 16) for generating brightness value data, an inner/outer conner-of-the-eye detection unit (reference point detection unit 17) for extracting a position of the reference image in which a vertical luminance value shows a steep change and an iris center detection unit (18) for extracting the centers of horizontal two points in the reference image.SELECTED DRAWING: Figure 1【課題】対象者の横方向の黒目位置を精度高く検出する。【解決手段】黒目位置検出装置（１）は、基準画像を生成するグラデーション処理部（１３）と、輝度値データを生成する輝度値データ生成部（輝度値グラフ生成部１６）と、縦方向輝度値が急峻な変化を示す基準画像の位置を抽出する目頭／目尻検出部（基準点検出部１７）と、基準画像の横方向の２点の中心を抽出する黒目中心検出部（１８）と、を備える。【選択図】図１
