PROBLEM TO BE SOLVED: To simply and accurately adjust rotation balance.SOLUTION: An X-ray CT apparatus in an embodiment comprises a rotation mechanism and a guide rail. The rotation mechanism rotates while holding an X-ray tube and an X-ray detector which detects X-rays emitted from the X-ray tube at a position opposite the X-ray tube. The guide rail is provided in at least a partial region along the rotation direction of the rotation mechanism and holds plural weights movably along the rotation direction.SELECTED DRAWING: Figure 1A
