Provided are a three-dimensional X-ray CT apparatus, a three-dimensional CT image reconstruction method, and a program, which are capable of reducing an operating time. A three-dimensional X-ray CT apparatus includes: a CT imaging portion for continuously and relatively rotating a measurement system with respect to a subject to perform a CT imaging measurement for taking data on a plurality of transmission images for reconstructing a three-dimensional CT image of the subject and an image reconstruction portion for reconstructing the three-dimensional CT image based on the data on the plurality of transmission images taken by the CT imaging portion and displaying the three-dimensional CT image. During a period in which the CT imaging measurement is being performed, the image reconstruction portion reconstructs the three-dimensional CT image based on already-taken data on transmission images and displays the three-dimensional CT image before the CT imaging measurement is completed.
