The apparatus includes: an X-ray source a multi slits element a first grating； a second grating； a driving section； a subject placing plate: and an X-ray detector, in which conversion elements to convert intensities of X-rays received thereby to electric signals, are arranged in a two-dimensional pattern so as to read the electric signals as image signals. The driving section moves the multi slits element relative to both the first grating and the second grating in a first direction orthogonal to a second direction of irradiating the X-rays, so that the X-ray detector repeats a processing for reading the electric signals converted from the intensities of X-rays received thereby, every time when the multi slits element moves at predetermined intervals so as to acquire the image signals representing Moire images captured at the predetermined intervals.
