To enhance the sensitivity of virus detection by polymerase chain reaction (PCR) and reverse-transcriptional (RT)-PCR, we developed a novel virus-concentration method using sulfonated (SO-) magnetic beads in the presence of divalent cations. In the presence of either Zn²⁺ or Cu²⁺ ions, we showed that SO-magnetic beads were able to concentrate non-enveloped model viruses, such as porcine parvovirus (PPV) and poliovirus, which were not concentrated by polyethyleneimine (PEI)-magnetic beads.¹⁾ Using the SO-magnetic beads, the sensitivity of virus genome detection by PCR or RT-PCR can be enhanced. Therefore, an efficient virus concentration method using either SO-magnetic beads or PEI-magnetic beads enhances the sensitivity of virus detection by PCR or RT-PCR.