1. A radiographic image detection apparatus comprising: a radiation source that outputs radiation to a subject; a radiographic image detector that obtains a radiographic image by detecting the radiation that has been output from the radiation source to the subject and that has passed through the subject; a relative-position changing means that moves at least one of the radiographic image detector and the subject to change the relative positions of the radiographic image detector and the subject with respect to each other; a defect-region storage means that stores the position of a defect region of the radiographic image detector; a region-of-interest setting means that sets a region of interest in the radiographic image detector; an overlap judgment means that judges whether the defect region stored in the defect-region storage means is included in the region of interest that has been set by the region-of-interest setting means; a movement amount calculation means that calculates a relative movement amount for changing the relative positions so that the defect region is not included in the region of interest when the overlap judgment means has judged that the defect region is included in the region of interest; and a movement control means that controls, based on the relative movement amount that has been calculated by the movement amount calculation means, an operation of the relative-position changing means for moving the at least one of the radiographic image detector and the subject.