An X-ray CT apparatus includes a fixed gantry having a plurality of stator coils arranged in a circle and mounted on the fixed gantry. A ring-shaped rotation frame of the CT apparatus includes a plurality of rotor magnets facing the plurality of stator coils. The CT apparatus further has an X-ray tube and an X-ray detector situated on the rotation frame to face each other and a supporting unit configured to provide non-contact support of the rotation frame on the fixed gantry. A magnetic pole detection unit of the apparatus is configured to detect a magnetic pole position of the rotor magnet at a start-up time of the plurality of stator coils and a brake mechanism of the apparatus is configured to apply a brake load to the rotation frame when detecting the magnetic pole position and to remove the brake load after detecting the magnetic pole position.