1. A measurement device comprising: an image pickup portion mounted in a mobile unit that outputs a plurality of images that are taken with a first view angle and that contain a measurement object and a plurality of images that are taken with a second view angle smaller than the first view angle and that contain the measurement object; a retrieval portion that retrieves, from at least two images taken with the second view angle by the image pickup portion, points that are each a feature point on the measurement object and that are in correspondence between the at least two images; a position/posture calculation portion that, on a basis of the plurality of images taken with the first view angle by the image pickup portion, calculates a relative relationship of a position and a posture of the image pickup portion occurring at each of times of image-taking of the plurality of images; a position/posture estimation portion that, on a basis of the relative relationships of the positions and the postures calculated by the position/posture calculation portion, estimates the relative relationships of the positions and the postures of the image pickup portion occurring at the times of image-taking of the at least two images with the second view angle; and a position measurement portion that measures a three-dimensional position of the points retrieved by the retrieval portion, on a basis of the retrieved points and the relative relationships of the positions and the postures estimated by the position/posture estimation portion.