A silicon drift detector for detecting radiation comprising: a first semiconductor part in which an electron and a hole are generated by incident radiation; a signal output electrode outputting a signal based on the electron or the hole; a gettering part gettering impurities in the first semiconductor part; and a second semiconductor part doped with a type of dopant impurities and having dopant impurity concentration higher than dopant impurity concentration of the first semiconductor part, wherein the second semiconductor part is in contact with the first semiconductor part, the gettering part is in contact with the second semiconductor part and not in contact with the first semiconductor part, the first semiconductor part has a plate-like shape, the second semiconductor part is located at one surface of the first semiconductor part and is formed of multiple curved electrodes made of p + type silicon, the other surface of the first semiconductor part is an entrance surface for incident radiation, at the entrance surface, a rear electrode made of p + type silicon serving as an electrode to which bias voltage is applied is formed on substantially the entire surface thereof, the gettering part is located on the second semiconductor part, the first semiconductor part and the signal output electrode are made of n-type silicon, and the constituent of the gettering part is made of n-type polysilicon, insulating parts are formed at portions of the first semiconductor part where the signal output electrode and the curved electrodes are not formed, a metal electrode is formed on the gettering part provided on each of the curved electrode closest to the signal output electrode and the curved electrode farthest from the signal output electrode, another metal electrode is formed on the signal output electrode, a voltage application part is connected to the metal electrode such that each of the curved electrodes has a potential varying in sequence from the curved electrode at the outer side to the curved electrode at the inner side, and the voltage application part is arranged to apply bias voltage to the rear electrode such that a potential difference occurs between the curved electrodes and the rear electrode. a first semiconductor part in which an electron and a hole are generated by incident radiation; a signal output electrode outputting a signal based on the electron or the hole; a gettering part gettering impurities in the first semiconductor part; and a second semiconductor part doped with a type of dopant impurities and having dopant impurity concentration higher than dopant impurity concentration of the first semiconductor part, wherein the second semiconductor part is in contact with the first semiconductor part, the gettering part is in contact with the second semiconductor part and not in contact with the first semiconductor part, the first semiconductor part has a plate-like shape, the second semiconductor part is located at one surface of the first semiconductor part and is formed of multiple curved electrodes made of p + type silicon, the other surface of the first semiconductor part is an entrance surface for incident radiation, at the entrance surface, a rear electrode made of p + type silicon serving as an electrode to which bias voltage is applied is formed on substantially the entire surface thereof, the gettering part is located on the second semiconductor part, the first semiconductor part and the signal output electrode are made of n-type silicon, and the constituent of the gettering part is made of n-type polysilicon, insulating parts are formed at portions of the first semiconductor part where the signal output electrode and the curved electrodes are not formed, a metal electrode is formed on the gettering part provided on each of the curved electrode closest to the signal output electrode and the curved electrode farthest from the signal output electrode, another metal electrode is formed on the signal output electrode, a voltage application part is connected to the metal electrode such that each of the curved electrodes has a potential varying in sequence from the curved electrode at the outer side to the curved electrode at the inner side, and the voltage application part is arranged to apply bias voltage to the rear electrode such that a potential difference occurs between the curved electrodes and the rear electrode.