1. A house change judgment method, comprising: a region-of-elevated-part extraction step of determining, based on altitude data on an above-ground surface including a feature, for each elevated part of the above-ground surface, a region of elevated part which contains each elevated part, the altitude data being acquired from above with regard to each point within a judgment target region, each elevated part having a size corresponding to a house to be a judgment target; an outline extraction step of extracting an outline of the house from the region of elevated part based on the altitude data; an object defining step of defining a house object containing three-dimensional information on the house based on the extracted outline and the altitude data within the outline; and a change judgment step of comparing a first object acquired at a first time point with a second object acquired at a second time point to detect a variation between the first object and the second object acquired at the two different time points, and making a judgment as to a house change based on the variation, wherein at least one of the first object and the second object is the house object.