An X-ray detection device comprising a sample holding unit, an X-ray irradiation unit (31, 32) 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 (31, 32), and the light transmitting plate includes: an opening portion for allowing the X-rays from the X-ray irradiation unit (31, 32), 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 (31, 32), 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 (31, 32), 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 (31, 32), and the light transmitting plate includes: an opening portion for allowing the X-rays from the X-ray irradiation unit (31, 32), 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 (31, 32), 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.