An anomalous enhancement of the NMR relaxation rate T1-1 was observed in the high-Tc superconducting state of the titled material at zero field, by using a field-cycling technique. The enhancement of T1-1 starts to pronounce below Tc∼6.2K, which was determined by AC susceptibility measurements on the same run. A peak of relaxation rate was observed much below Tc. The enhancement is suppressed by the external field, which evidences a close relation to the superconductivity.