An object of the invention is to provide a high-resolution transmission type X-ray tube. With an X-ray imaging device according to the present invention, electron lens forming part 100A includes a central axis part 131, which is formed at the interior of a yoke 130, and an outer peripheral part 133, which defines the outer periphery of yoke 130. A part of a front end part 135 of central axis part 131 becomes a magnetic pole 110 that is positioned at the side of an electron gun. A first opening 111 is defined by magnetic pole 110. A part of a front end part 137 of outer peripheral part 133 becomes a magnetic pole 120 that is positioned at the side of a target 300. A second opening 121 is defined by magnetic pole 120. The value of diameter d2 of second opening 121 is greater than the value of diameter d1 of first opening 111.