An accurate non-destructive inspection of a moving subject is conducted using a radiation source unit that irradiates radioactive rays toward gratings. Each grating includes a plurality of grating members. A radioactive ray detector unit detects the radioactive rays diffracted by the plurality of grating members. The plurality of grating members are arranged with a predetermined phase difference such that moiré pattern images respectively formed by the radioactive rays transmitted through first to third partial areas have a phase difference between the moiré pattern images.