A moving object contour tracking apparatus(2000) includes a contour tracking section (2010) for performing, by taking an initial contour of the moving object in a predetermined image slice as a starting contour, contour tracking in a first time direction to acquire a first contour of the moving object and contour tracking in a second time direction to acquire a second contour of the moving object in each image slice a contour comparison section (2020) for calculating, in the predetermined image slice, a similarity between the first contour and the initial contour and a similarity between the second contour and the initial contour and a contour correction section (2030) for taking the contours in the image slices that are acquired in a contour tracking direction corresponding to the greater one of the two similarities as the contours of the moving object in the respective image slices.
