The capsule medical device 10 in the in-vivo information acquisition system 1 includes an illuminating unit 13 that illuminates the inside of the subject 100, and an effective pixel region Reff on which an optical image in the subject 100 illuminated by the illuminating unit 13 is formed. The imaging unit 12 having an OB region ROB in which the optical image is shielded, and the light from the illumination unit 13 based on the pixel value of the image signal in the effective pixel region Reff and the pixel value of the image signal in the OB region ROB A dimming control unit (16, 17, 18) for dimming the amount of light.生体内情報取得システム１におけるカプセル型医療装置１０は、被検体１００内を照明する照明部１３と、照明部１３で照明された被検体１００内の光学像が結像される有効画素領域Ｒｅｆｆと、光学像が遮光されるＯＢ領域ＲＯＢと、を有する撮像部１２と、有効画素領域Ｒｅｆｆの画像信号の画素値とＯＢ領域ＲＯＢの画像信号の画素値とに基づいて照明部１３からの光の光量を調光する調光制御部（１６，１７，１８）と、を備える。
