A radiation generating apparatus includes: an envelope 1 having a first window 2 through which a radiation is transmitted; and a radiation tube 10 being held within the envelope 1, and having a second window 15 which is arranged in opposition to the first window 2, and through which the radiation is transmitted; and a radiation shielding member 16 thermally connected to the second window 15, having a radiation transmitting hole 21 arranged in communication with the second window 15, and having a protruding portion protruding from the second window 15 toward the first window 2. A thermal conducting member 17 having a higher thermal conductivity rather than that of the radiation shielding member 16 is connected to the protruding portion of the radiation shielding member 16. The radiation generating apparatus can shield an unnecessary radiation and cool a target with a simple structure and is entirely reduced in weight.