Abstract: A first X-ray image is obtained by imaging a target in a first direction and at a first elevation angle, and a second X-ray image is obtained by imaging the target in a second direction and at a second elevation angle. Based on these two X-ray images, cross-section data of the target is obtained. The first and second X-ray images are converted into first and second thickness data, and first cross-section data based on a first surface side of the target and second cross-section data based on a second surface side of the target are obtained based on the first thickness data. Similar third cross-section data and four cross-section data are obtained based on the second thickness data. The cross-section data of the target is obtained by partially extracting and synthesizing cross-section data of a highly reliable region from these pieces of cross-section data.