According to one embodiment, an X-ray CT apparatus includes a data acquiring unit, a data processing unit and a data transmitting unit. The data acquiring unit is configured to expose an X-ray to an object, acquire detection data of the X-ray having transmitted the object and compress the detection data to generate compressed data. The data processing unit is configured to generate X-ray CT image data of the object based on the compressed data transmitted from the data acquiring unit through a transmission line. The data transmitting unit is configured to transmit uncompressed detection data of an X-ray to the data processing unit through the transmission line according to information from an input device.
