In this paper, we have investigated the tidal characteristics of the Nakdongpo estuary. We have carried out the analysis of harmonic constant with the use of the recorded data on tidal level at the Gadeong Do tide station and analyzed the flow velocity data obtained by ourselves at two points in the Nakdongpo estuary. In addition, we have analyzed the variation of the mean-sea level. Typical items of the characteristics we have found are; (1) The principal harmonic constants and non-harmonic constants are shown in table 2. (2) Tide in this area shows the semidiurnal inequality. (3) The mean-sea level is shown to be depressed at the rate of about 1cm to the rise of 1 mbar of the atmospheric pressure. (4) (i) At K2 point, The E-W component of the velocty reveals the nature of progressive waves. The N-S component reveals the nature of stationary waves. (ii) At K3 point, The E-W component shows the characteristics of progressive waves to some degree. The N-S component shows a weak hint of stationary waves. (5) At K2 point, S-component is predominant due to the flow of river. At K3 point, E-component is predominant due to the Tsushima current.