1. A three-dimensional modeling apparatus comprising: means for calculating relative positions among a plurality of cameras by using captured images of a reference object for detecting each camera position, the images being obtained from the plurality of cameras; and means for producing a three-dimensional model of a target object from captured images, obtained from the plurality of cameras, of the target object on a turntable having reference marks for detecting position provided thereon, the modeling target rotating with the turntable, wherein the means for producing a three-dimensional model calculates, based on images captured by a camera which captures images of the turntable, position information with respect to the turntable and the camera; the means for producing a three-dimensional model further calculates, using the position information and the relative position obtained by the means for calculating relative positions, position information with respect to the turntable and a camera which does not capture images of the turntable; and a three-dimensional model of the modeling target is produced based on the obtained position information of each camera and images captured by each camera.