The removal of radioactive Cs-137 from contaminated soil and water is urgently needed in Japan. Rhodococcus erythropolis CS98 strain possesses a higher ability for cesium accumulation than previously-reported microorganisms. Immobilization of CS98 strain in polymer supports shows promise for efficient cesium removal. In this study, we compared agarose gel and 3 types of PVA gels for CS98 strain immobilization. We clarified that (i) the mechanical strength of the PVA gels was higher than that of agarose gel, (ii) CS98 strain immobilized in agarose gel could accumulate radioactive Cs-137, and (iii) the ability of the strain for radioactive cesium accumulation was higher in agarose gel than in PVA gels. These results demonstrate that agarose gel is more promising as a polymer support material for CS98 strain than PVA gels.