An X-ray imaging apparatus which obtains an X-ray image, the apparatus includes: imaging means (103) including a plurality of detecting elements for converting X-rays generated by an X-ray generating apparatus which outputs or stops X-rays in accordance with an operation instruction into an image signal and obtaining means (105) for obtaining an operation start timing of the X-ray generating apparatus based on an image signal output from the imaging means and obtaining a difference between a timing of an operation instruction to the X-ray generating apparatus and the operation start timing.
