PROBLEM TO BE SOLVED: To prevent an alarm signal from being erroneously output with respect to a fine-eye condition caused by direct light. SOLUTION: A driver monitor 100 (occupant monitoring device) performs an predetermined process on an image capturing unit 11 that captures a face of an occupant of a vehicle and a face image captured by the image capturing unit 11, and the occupant from the face image. Image processing unit 2 for extracting the eyes, an opening/closing degree calculation unit 31 for calculating an opening/closing degree indicating the opening/closing state of the eyes based on the image of the eyes extracted by the image processing unit 2, and a predetermined region in the face image. The weight calculation unit 33 that calculates a weight according to the luminance information of the, and the opening and closing degree calculated by the opening and closing degree calculation unit 31 are weighted by the weight, and the eye opening and closing degree is calculated based on the weighted opening and closing degree. An open/close state determination unit 34 that determines the open/closed state and an alarm output unit 35 that outputs an alarm signal based on the determination result of the open/close state determination unit 34 are provided. [Selection diagram] Figure 1【課題】直射光に基因する細眼状態に対して、誤って警報信号が出力されるのを防止する。【解決手段】ドライバモニタ１００（乗員監視装置）は、車両の乗員の顔を撮像する撮像部１１と、この撮像部１１が撮像した顔画像に対して所定の処理を行い、当該顔画像から乗員の眼を抽出する画像処理部２と、この画像処理部２で抽出された眼の画像に基づいて、眼の開閉状態を表す開閉度を算出する開閉度算出部３１と、顔画像における所定領域の輝度情報に応じた重みを算出する重み算出部３３と、開閉度算出部３１で算出された開閉度に対して、前記重みにより重み付けを行い、当該重み付けがされた開閉度に基づいて眼の開閉状態を判定する開閉状態判定部３４と、この開閉状態判定部３４での判定結果に基づいて警報信号を出力する警報出力部３５とを備えている。【選択図】図１
