In the case where variations in ground objects in one and the same area are detected between a line drawing map describing profile lines of the ground objects or a reference line drawing/image obtained by picking up the ground objects from above, and a target image obtained by picking up the ground objects in the same area from above later on, a variation detecting apparatus collates the reference line drawing/image with the target image so as to obtain variation indexes indicating whether there are variations or not in the ground objects respectively, and displays ground objects which can be judged to have variations or ground objects which cannot be judged as to whether there are variations or not on the basis of the variation indexes, in a display mode in which an area of the reference line drawing/image including the ground objects and an area of the target image including the ground objects can be compared with each other. Accordingly, confirmation or update of variations of ground objects on a line drawing map can be coped with easily, and portions having variations can be selectively displayed so that portions where variation detection should be confirmed can be understood intuitively.