An image capturing apparatus previously captures a calibration image that serves as a reference when a distance to an object is calculated, and calculates, when an image of the object is captured using a monocular camera, the distance from the lens of the camera to the object using the calibration image and the distance from the lens of the camera to the calibration image. In this case, the image capturing apparatus measures the distance from the lens of the camera to one or more arbitrary points on the object, calculates the diffuse reflection coefficient of the object using the measured distance, the luminance on each of one or more arbitrary points, the distance to the calibration image, and the luminance, and calculates the distance to the object from the lens of the camera to the object using the calculated diffuse reflection coefficient.