An X-ray detection device comprising a sample holding unit , an X-ray irradiation unit for irradiating a sample held on the sample holding unit with X-rays, an X-ray detection unit for detecting X-rays generated from the sample , an illumination unit for irradiating the sample with light, and an observation unit for observing the sample , the X-ray detection device comprising: a light transmitting plate for allowing the light from the illumination unit , with which the sample held on the sample holding unit is irradiated, to be transmitted therethrough; a vacuum chamber ; and an X-ray transmitting film , wherein the light transmitting plate is disposed at a position between the sample holding unit and the X-ray irradiation unit , and the light transmitting plate includes: an opening portion for allowing the X-rays from the X-ray irradiation unit , with which the sample is irradiated, to pass therethrough; and wherein the X-ray transmitting film covers the opening portion , at least part of each of the X-ray irradiation unit , the X-ray detection unit and the illumination unit is disposed inside the vacuum chamber , the light transmitting plate is part of the wall of the vacuum chamber , and the sample holding unit is disposed outside the vacuum chamber (2, , and wherein the light transmitting plate is characterized by including a scattering portion for scattering light transmitted therethrough, wherein the scattering portion is irradiated with light from the illumination unit , the light is scattered when transmitted through the scattering portion , and the sample is irradiated with the light scattered at the scattering portion , and the light reflected by the sample passes through the opening portion and enters the observation unit . the X-ray detection device comprising: a light transmitting plate for allowing the light from the illumination unit , with which the sample held on the sample holding unit is irradiated, to be transmitted therethrough; a vacuum chamber ; and an X-ray transmitting film , wherein the light transmitting plate is disposed at a position between the sample holding unit and the X-ray irradiation unit , and a light transmitting plate for allowing the light from the illumination unit , with which the sample held on the sample holding unit is irradiated, to be transmitted therethrough; a vacuum chamber ; and an X-ray transmitting film , wherein the light transmitting plate is disposed at a position between the sample holding unit and the X-ray irradiation unit , and the light transmitting plate includes: an opening portion for allowing the X-rays from the X-ray irradiation unit , with which the sample is irradiated, to pass therethrough; and wherein the X-ray transmitting film covers the opening portion , at least part of each of the X-ray irradiation unit , the X-ray detection unit and the illumination unit is disposed inside the vacuum chamber , the light transmitting plate is part of the wall of the vacuum chamber , and the sample holding unit is disposed outside the vacuum chamber (2, , and wherein the light transmitting plate is characterized by including a scattering portion for scattering light transmitted therethrough, wherein the scattering portion is irradiated with light from the illumination unit , the light is scattered when transmitted through the scattering portion , and the sample is irradiated with the light scattered at the scattering portion , and the light reflected by the sample passes through the opening portion and enters the observation unit . <EOS>