In an inspection of an object of inspection with use of X-rays, X-rays are output from an X-ray source disposed fixedly into a range of a predetermined solid angle and, while the object of inspection is moved along a plane within the output range of the X-rays, the X-rays are detected, in positions included in the solid angle and at a plurality of revolved points around an axis oriented vertical to the plane along which the object of inspection is moved, with its detecting surface tilted down toward the axis. Thus, the object can be inspected based on the detected X-rays.