A beam irradiation target verification apparatus (1) includes an X-ray switching emission process unit (6a) that causes a vertical X-ray emitting unit (13) to emit at least two types of X-rays using an energy-level switching unit (11), a vertical X-ray detection unit (14) that detects an X-ray emitted from the vertical X-ray emitting unit (13), a pre-therapy verification image generation process unit (7) that generates pre-therapy verification images (20B) and (20C) based on detection information on at least two types of X-rays obtained by the vertical X-ray detection unit (14), a reference image acquisition unit (3) that acquires a reference image (20A) obtained at a therapy planning stage, a comparison process unit (8a) that makes comparisons between the pre-therapy verification images (20B) and (20C) and the reference image (20A), and a result output unit (4) that outputs a comparison result obtained by the comparison process unit (8a). Thus, there is provided a beam irradiation target verification apparatus for therapeutic purposes capable of measuring internal conditions of a therapy patient and determining necessity of changing a therapy plan, easily and at a relatively low exposure level.
