An X-ray inspection method for computing a cross-sectional shape of a three-dimensional target having a first surface and a second surface facing the first surface by transmitting X-rays through the target using an X-ray source for radiating X-rays, an X-ray detector for detecting the X-rays and a computing device, comprising: arranging the X-ray source in a predetermined first direction and at a predetermined first elevation angle with respect to the target and the X-ray detector to face the X-ray source across the target and, in this state, causing the X-rays to be radiated from the X-ray source and the X-ray detector to obtain a first X-ray image of the target; arranging the X-ray source in a second direction different from the first direction and at a predetermined second elevation angle with respect to the target and the X-ray detector to face the X-ray source across the target and, in this state, causing X-rays to be radiated from the X-ray source and the X-ray detector to obtain a second X-ray image of the target; causing the computing device to compute first thickness data of the target viewed in the first direction and in a direction of the first elevation angle based on a luminance value distribution of the first X-ray image along the first direction and further compute first cross-section data based on the first surface side of the target and second cross-section data based on the second surface side based on the first thickness data; causing the computing device to compute second thickness data of the target viewed in the second direction and in a direction of the second elevation angle based on a luminance value distribution of the second X-ray image along the second direction and further compute third cross-section data based on the first surface side of the target and fourth cross-section data based on the second surface side based on the second thickness data; and causing the computing device to partially extract cross-section data of a highly reliable region determined by the first and second directions from the first to fourth cross-section data and derive cross-section data of the target by synthesizing the extracted pieces of partial cross-section data. arranging the X-ray source in a predetermined first direction and at a predetermined first elevation angle with respect to the target and the X-ray detector to face the X-ray source across the target and, in this state, causing the X-rays to be radiated from the X-ray source and the X-ray detector to obtain a first X-ray image of the target; arranging the X-ray source in a second direction different from the first direction and at a predetermined second elevation angle with respect to the target and the X-ray detector to face the X-ray source across the target and, in this state, causing X-rays to be radiated from the X-ray source and the X-ray detector to obtain a second X-ray image of the target; causing the computing device to compute first thickness data of the target viewed in the first direction and in a direction of the first elevation angle based on a luminance value distribution of the first X-ray image along the first direction and further compute first cross-section data based on the first surface side of the target and second cross-section data based on the second surface side based on the first thickness data; causing the computing device to compute second thickness data of the target viewed in the second direction and in a direction of the second elevation angle based on a luminance value distribution of the second X-ray image along the second direction and further compute third cross-section data based on the first surface side of the target and fourth cross-section data based on the second surface side based on the second thickness data; and causing the computing device to partially extract cross-section data of a highly reliable region determined by the first and second directions from the first to fourth cross-section data and derive cross-section data of the target by synthesizing the extracted pieces of partial cross-section data.