An X-ray waveform is generated by validating detection data corresponding to when an X-ray (4) is generated at a collision point (9) among X-ray detection data and invalidating other data. For example, when laser light (3) is pulse laser light and an electron beam (1) is a continuous electron beam or a pulse-like electron beam having a pulse width equal to or greater than that of the pulse laser light, the X-ray waveform is generated by detecting the laser light (3) and multiplying the X-ray detection data by laser light detection data after making time axes coincident with respect to the collision point (9).