Abstract: An image processing device includes: a control unit configured to acquire a cross-sectional image obtained using a sensor configured to move in a lumen of a biological tissue for each position in a movement direction of the sensor, analyze the acquired cross-sectional image to calculate a centroid position of a cross section of the lumen in the cross-sectional image, and execute smoothing on a calculation result obtained for a plurality of positions in the movement direction of the sensor, and evaluate a difference between the calculated centroid position and a centroid position obtained as a result of the smoothing for each position in the movement direction of the sensor, thereby deriving a pulsation score representing expansion and contraction of the lumen in the acquired cross-sectional image by a numerical value.