1. A method for measuring an object based on images comprising: capturing the images by plural cameras; using more image information obtained from an image in a photographing area common to the images captured by the cameras than image information obtained from an image in an area other than the common photographing area to set camera parameters; using the set camera parameters to photograph the same photographing areas as those when the camera parameters are set so as to capture images anew, the photographing being performed by the cameras; determining corresponding points in the newly captured images; and obtaining three-dimensional information of the object included in a photographing area.