A grip portion configured to support a test piece is disposed at a central part of a base, and a plurality of pillars are erected on the base. A disposition and number of the plurality of pillars are adjusted so that an X-ray emitted from an X-ray source and transmitting through the test piece transmits through zero or one pillar in an optional image capturing direction. It is possible to avoid a situation in which an attenuation rate of the X-ray largely differs due to a difference in an image capturing direction to the test piece. Thus, it is possible to prevent a strong artifact from overlapping a CT image of the test piece in an X-ray CT image. Moreover, a material testing machine is supported by the plurality of pillars to have an accessible state around the test piece. This configuration facilitates handling of the material testing machine.