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 configured to be irradiated with an electron beam； an electron emitting source configured to irradiate the transmission target with the electron beam obliquely； and a tubular forward shield member 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 surface and a projection of the central axis of the electron beam to the surface.
