A beam irradiation target verification apparatus includes an X-ray switching emission process unit that causes a vertical X-ray emitting unit to emit at least two types of X-rays using an energy-level switching unit, a vertical X-ray detection unit that detects an X-ray emitted from the vertical X-ray emitting unit, a pre-therapy verification image generation process unit, a reference image acquisition unit that acquires a reference image obtained at a therapy planning stage, a comparison process unit. The pre-therapy verification image generation process unit to generate pre-therapy verification images based on detection information of at least two types of X-rays obtained by the vertical X-ray detection unit. The comparison process unit makes comparisons between the pre-therapy verification images and the reference image, and the result output unit outputs a comparison result obtained by the comparison process unit.