The present invention provides an X-ray generating tube including a transmission target having a minute focal spot. The X-ray generating； tube includes a transmission target having a first surface and a second surface opposite to the first surface, the first surface being irradiated with an electron beam, and the target radiating X-rays from the second surface； an electron emitting source emitting the electron beam in such a manner that the electron beam obliquely enters the first surface； and a tubular forward shield member located at the second surface side of the target to define an extraction angle of an extracted X-ray beam. The forward shield member is disposed such that a central axis of the electron beam and a central axis of the X-ray beam whose extraction angle is defined are located at the same side with respect to a virtual normal plane perpendicular to the first surface and a projection central axis that is a projection of the central axis of the electron beam to the first surface.
