Quasi-periodic variation of cosmic radio noise absorption (called CNA pulsation), measured by a fast-response 30-MHz riometer at Syowa Station in Antarctica (L~6), was examined. CNA pulsations with the period of 10--500 s are observed mostly during morning hours. Most of the CNA pulsations are associated with magnetic pulsations and quasi-periodic (QP) VLF emissions. The examination of the relationships among CNA pulsation, QP emission, and magnetic pulsation, using the cross-correlation analysis method, shows that some CNA pulsations with the period of 10--500 s are well related to magnetic pulsations and QP emissions. In these cases, CNA pulsations are more correlated with the D component of magnetic pulsations than with H component. It is also shown that the phase of the CNA pulsation lags behind QP emissions by 60--120¿ independent of pulsation period.