A first angle α formed between a direction normal to a white board (100) that is disposed along a plurality of reinforcing bars (2) and an imaging direction of a camera (200) and a second angle β indicating the direction of the reinforcing bar 2 which is a measurement target with respect to the imaging direction of the camera (200) are detected. In addition, a first distance D1 between the camera (200) and the white board (100) is measured by a laser distance meter provided in the camera (200). The amount of deviation D2 of the reinforcing bar (2) in the imaging direction of the camera (200) with respect to the first distance D1 is calculated on the basis of the measured first distance D1, the detected first angle α, and the detected second angle β.