There is provided a radiation generating apparatus having a simple structure and capable of shielding unnecessary radiation, cooling a target, reducing the size and weight of the apparatus, and achieving higher reliability, and a radiation imaging apparatus having the same. A transmission type radiation tube is held inside a holding container filled with a cooling medium. The transmission type radiation tube includes an envelope having an aperture, an electron source arranged inside the envelope so as to face the aperture of the envelope, a target unit for generating a radiation responsive to an irradiation with an electron emitted from the electron source, and a shield member for shielding a part of the radiation emitted from the target unit. The cooling medium contacts at least a part of the shield member.