To provide an action monitoring system capable of minimizing an adverse effect of a physical constitution of a person to be monitored on determining whether the person to be monitored has performed a predetermined action.SOLUTION: An action monitoring system 10 includes an acquisition unit 11 that acquires a distance image of which pixel value represents a distance to an object of imaging which is a space encompassing a person to be monitored 40 and a bed 30, a detection unit 16 that detects the height of the head of the person to be monitored 40 using three-dimensional point group data obtained by performing coordinate transformation on the acquired distance image, a calculation unit 18 that calculates a threshold on the basis of the detected height of the head of the person to be monitored 40, and a determination unit 17 that compares the height of the head of the person to be monitored 40, which is obtained with a bed surface 30a of the bed 30 as a reference, with the threshold, and thus determines whether the person to be monitored 40 has performed a predetermined action.SELECTED DRAWING: Figure 2【課題】被監視者が所定の行動を行ったか否かの判定において、被監視者の体格の影響を低減することができる行動監視装置を提供する。【解決手段】行動監視装置１０は、被監視者４０、及び、ベッド３０を含む空間を撮像対象とする、画素値が撮像対象までの距離を示す距離画像を取得する取得部１１と、取得された距離画像を座標変換処理することで得られる三次元点群データを用いて被監視者４０の頭部の高さを検出する検出部１６と、検出された被監視者４０の頭部の高さに基づいて閾値を算出する算出部１８と、ベッド３０のベッド面３０ａを基準とした被監視者４０の頭部の高さと閾値とを比較することにより被監視者４０が所定の行動を行ったか否かを判定する判定部１７とを備える。【選択図】図２
