1. An X-ray CT device provided with an X-ray source that generates X-ray beams spreading along the body axis of a patient, an X-ray detecting unit in which detection elements for detecting X-rays that pass through the patient are arranged in a plurality of rows along the body axis of the patient, and a reconstructing unit for reconstructing an image from data detected by the X-ray detecting unit, the X-ray CT device comprising: a scan controlling unit for performing control in such a manner that first projection data is acquired by moving the X-ray source and the patient in a relative manner to each other along the body axis of the patient and second projection data is acquired by rotating the X-ray source around the patient; a reconstruction processing unit for performing a reconstruction process by combining the first projection data and the second projection data; and a determining unit for determining whether a scan should be performed or whether the reconstruction process should be performed, based on a scan condition of the first projection data and a scan condition of the second projection data.