To provide a radiation shield and a radioactive material containment vessel excellent in construction property and having little shielding defect, without causing an increase in thickness of the radiation shield.

The radiation shield comprises a plurality of split main blocks arranged with the ends of adjacent main blocks opposite to each other. Cutouts whose surfaces have curved cross sections are provided crosswise on one or both surfaces at the ends of adjacent main blocks 21a, 21b, and the adjacent main block 21a, 21b are arranged with the tips of their ends opposite to each other to form grooves 20 in the form of curved faces. Auxiliary blocks 22 in the form of curved faces corresponding to the grooves 20 are embedded into the grooves 20 to form a joint structure. The radiation shield having such a joint structure has little shielding defect, and the radioactive material containment vessel uses the radiation shield.