A data acquisition device, which has an X-ray detector including a plurality of channel widths at which channels at its central portion are fine and channels at its peripheral portions are coarse or rough, and a plurality of data acquisition ranges including a data acquisition range wide in a channel direction and a data acquisition range narrow in the channel direction, and which is capable of performing switching among the data acquisition ranges for each data acquisition, is used to perform data acquisition on the channels fine at the central portion in the data acquisition range narrow in the channel direction, whereby an X-ray CT apparatus is provided which is capable of performing high-resolution imaging and brings about more satisfactory image quality.