Dependence of the standard deviation of wind direction fluctuations, $sigma_ heta$, on atmospheric stability, averaging time and topography were analysed with the data measured at three sites, Youngjongdo beach of the Yellow Sea, Chuncheon basin and Doam-Dam valley. The results show that the mean value of $sigma_ heta$ is large in complex terrain, the Doam-Dam site. It is notable that the large value of $sigma_ heta$ at night is associated with the low wind speed and the strong stable condition. In order to study the long-period fluctuations of the wind direction, $sigma_ heta$ for longer than 10 minutes averaging time was further analysed using the data obtained at the Chuncheon basin. At the averaging time shorter than 60 minutes, larger $sigma_ heta$ is associated with longer averaging time in the strong stable condition. However, $sigma_ heta$ was not affected significantly by wind speed and averaging time in neutral conditions. The results of the spectrum analysis for the time series data of wind direction showed that low-frequency fluctuations ranging from 10 to 60 minutes were dominated at the Chuncheon basin in strong stable condition.