A radiation generating apparatus comprising: an envelope having a first window through which a radiation is transmitted; a radiation tube being held within the envelope, and having a second window which is arranged in opposition to the first window, and through which the radiation is transmitted, wherein the radiation tube has an electron emitting source arranged at an inside of the radiation tube; a target emitting a radiation in response to an irradiation with an electron emitted from the electron source; a substrate on which the target is formed at a side of the substrate opposing the electron emitting source, and the second window is formed in the substrate; and a radiation shielding member having a first shielding member with an electron beam transmitting hole in communication with the second window, and a second shielding member with a radiation transmitting hole in communication with the second window, wherein the first shielding member is placed to protrude from the second window toward the electron emitting source, and the second shielding member is placed to protrude from the second window toward the first window; and a thermal conducting member; wherein the thermal conducting member having a higher thermal conductivity than that of the radiation shielding member is connected to the second shielding member, the thermal conducting member and the second shielding member have cylindrical shapes having the same central axis, the thermal conducting member is placed on an inner peripheral side of the second shielding member protruding from the second window toward the first window, and the thermal conducting member has a lower density than that of the radiation shielding member. an envelope having a first window through which a radiation is transmitted; a radiation tube being held within the envelope, and having a second window which is arranged in opposition to the first window, and through which the radiation is transmitted, wherein the radiation tube has an electron emitting source arranged at an inside of the radiation tube; a target emitting a radiation in response to an irradiation with an electron emitted from the electron source; a substrate on which the target is formed at a side of the substrate opposing the electron emitting source, and the second window is formed in the substrate; and a radiation shielding member having a first shielding member with an electron beam transmitting hole in communication with the second window, and a second shielding member with a radiation transmitting hole in communication with the second window, wherein the first shielding member is placed to protrude from the second window toward the electron emitting source, and the second shielding member is placed to protrude from the second window toward the first window; and a thermal conducting member; wherein the thermal conducting member having a higher thermal conductivity than that of the radiation shielding member is connected to the second shielding member, the thermal conducting member and the second shielding member have cylindrical shapes having the same central axis, the thermal conducting member is placed on an inner peripheral side of the second shielding member protruding from the second window toward the first window, and the thermal conducting member has a lower density than that of the radiation shielding member.