In this paper, a new camera calibration method without a test object to be measured is described. This method has been developed for a camera mounted on a mobile robot. The 3 edges at the corner of a room or a building are adopted as the 3 world axes. First, our method calculates the 3 rotational parameters using these 3 edges. Second, the 3 translational parameters are calculated using 2 or more than 2 reference points that are assumed to exist near the corner. Finally, experiments using over the counter goods are executed in order to ensure the efficiency of our method.