Impurity effects on NaxCoO2�yH2O are studied by Mn doping. Spectroscopic evidence reveals that the doped Mn ions occupy the Co sites and the valence is +4. The magnetic local moment induced by Mn doping was observed and . The induced local moment could lead to magnetic pair-breaking and is likely to be responsible for the Tc suppression by Mn impurities in NaxCo1-zMnzO2�yH2O.