1. An image processing apparatus detecting an edge of a detection-target subject imaged by an image pickup device having line-defect pixels, the line-defect pixels being line defect(s) in one or both of a horizontal direction and a vertical direction, the apparatus comprising: rotating motor configured to rotate the image pickup device or the detection-target subject; and a control apparatus configured to: image, in a single imaging, the detection-target subject with the image pickup device, with the image pickup device or the detection-target subject being rotated by the rotating motor at a predetermined angle so that the edge of the detection-target subject is not parallel to each of horizontal and vertical scanning lines of the image pickup device, and detect the edge of the detection-target subject by performing sub-pixel processing on a gray-scale image obtained by performing correction by interpolation on a luminance of each of the line-defect pixels with luminances of pixels adjacent to both sides of the line-defect pixel based on the single imaging, wherein when bumps of a Ball Grid Array-type component are taken as the detection-target subject and an edge of each of the bumps is detected, the control apparatus is configured to rotate at the predetermined angle so that an arrangement of the bumps in longitudinal, lateral, and diagonal directions of the Ball Grid Array-type component is not parallel to each of the horizontal and vertical scanning lines of the image pickup device.