US Patent 9188553 X-ray fluorescence analyzer

An X-ray fluorescence analyzer includes a sample stage having an opening at an X-ray irradiation position, an X-ray source which irradiates a sample placed on the opening with a primary X-ray from below, a detector which detects an X-ray fluorescence generated from the sample, a transparent drop prevention plate supported to be advanced and retracted immediately below the opening, a drive mechanism which advances and retracts the drop prevention plate, an observation camera which observes the drop prevention plate positioned immediately below the opening, and an operation unit which processes an image of the drop prevention plate which is captured by the observation camera. The operation unit detects a foreign matter on the drop prevention plate based on an image difference between images before and after the drive mechanism moves or vibrates the drop prevention plate within an observation range of the observation camera.