Tidal exchange of sea water was studied by using drogue experiments and tidal current measurement data in Yeoja Bay which has a narrow channel. At the spring tide, the volume of tidal transport in the bay was estimated to be 43% of the mean volume of the sea water in Yeoja Bay, 1.96km super(3). Residual current was deduced to flow southward at the rate of 3,658$ imes$10 super(4) m super(3) per tidal cycle. The mean tidal exchange of sea water during the flood flow was estimated to be approximately 5.0% of the volume of sea water at the mean high water level in the bay, 2.33km super(3), while that during the ebb flow was 6.3%. One dimensional diffusion coefficient of 1.69-1.97$ imes$10 super(6) cm super(2)/sec was obtained at the channel in the bay.