An imaging controller of a CT imaging apparatus, the imaging apparatus including first and second imagers (371, 372), wherein each imager (371, 372) is a combination of a diagnostic x-ray source (341, 342) and a sensor array (361, 362), for capturing a radiographic image by emitting a cone beam toward a rotation axis and a rotation mechanism for rotating the first and second imagers (371, 372) integrally around the rotation axis and in which an angle between an irradiation axis of the first imager and an irradiation axis of the second imager with the rotation axis as a reference is a predetermined angle, the imaging controller comprising: an imager position determination section adapted to determine whether or not the first imager is located in an overlapping region where a rotation range of the first imager and a rotation range of the second imager overlap each other when the rotation mechanism rotates the first and second imagers (371, 372) by an angle greater than the predetermined angle; an imaging timing control section adapted to cause one or both of the first and second imagers (371, 372) to perform imaging when arrival of an imaging timing is detected and to cause only the second imager to perform imaging in at least one imaging timing whose arrival is detected in a state where the imager position determination section determines that the first imager is located in the overlapping region; and a position specifying section adapted to specify a three-dimensional position of a position specification target based on a radiographic image captured by the first imager and a radiographic image captured by the second imager, characterized in that the imaging timing control section is further adapted to perform the following: when the imaging timing control section detects arrival of an imaging timing and causes both of the first and second imagers (371, 372) to perform imaging and the position specifying section fails to detect an image of the position specification target in at least one of the obtained radiographic images to thereby fail to specify the three-dimensional position of the position specification target, the imaging timing control section causes only the second imager to perform imaging at a predetermined number of imaging timings in a state where the imager position determination section determines that the first imager is located in the overlapping region. an imager position determination section adapted to determine whether or not the first imager is located in an overlapping region where a rotation range of the first imager and a rotation range of the second imager overlap each other when the rotation mechanism rotates the first and second imagers (371, 372) by an angle greater than the predetermined angle; an imaging timing control section adapted to cause one or both of the first and second imagers (371, 372) to perform imaging when arrival of an imaging timing is detected and to cause only the second imager to perform imaging in at least one imaging timing whose arrival is detected in a state where the imager position determination section determines that the first imager is located in the overlapping region; and a position specifying section adapted to specify a three-dimensional position of a position specification target based on a radiographic image captured by the first imager and a radiographic image captured by the second imager, characterized in that the imaging timing control section is further adapted to perform the following: when the imaging timing control section detects arrival of an imaging timing and causes both of the first and second imagers (371, 372) to perform imaging and the position specifying section fails to detect an image of the position specification target in at least one of the obtained radiographic images to thereby fail to specify the three-dimensional position of the position specification target, the imaging timing control section causes only the second imager to perform imaging at a predetermined number of imaging timings in a state where the imager position determination section determines that the first imager is located in the overlapping region.