A radiation generating tube 1 includes: an electron emitting source 3; a target 9 spaced from the electron emitting source 3, for generating radiation 11 responsive to irradiation with an electron beam from the electron emitting source 3; and a tubular shielding member 10 having an electron passing hole 8, wherein the electron passing hole 8 has an electron incident aperture at one end thereof and has a target supporting surface 9b supporting the target 9 at the other end thereof, wherein the target supporting surface 9b is connected through a brazing filler 14 to a periphery of a surface of the target at a side on which the electron is incident, and an opening size of the other end of the electron passing hole 8 is larger than an opening size of the electron incident aperture at the one end thereof.