A storage unit 2 arranged on a foot side of a subject placed on a top board is provided with a box composed of a block member 22 and a plate member 23 and a lid 21 covering an upper side of the box. The lid 21 is provided so as to be capable of pivoting about a shaft 20 relative to the plate member 23 of the box composed of the block member 22 and the plate member 23. When the lid 21 is in a closed state, the upper portion of the plate member 23 of the box composed of the block member 22 and the plate member 23 is covered by the lid 21. In this state, as shown in FIG. 2, the upper surface of the lid 21 and the surface of the top board of the storage unit 2 are arranged at the same height, and are thus coplanar.
