Fine sediment transport, Ariake Bay, numerical model, tidal current. The transport of fine sediment, i.e., silt and clay, has a key role in estuarine and coastal environments. In this study, the fine sediment transport processes in Ariake Bay are elucidated through the analysis of field data and a preliminary numerical simulation of the transport processes. The numerical model uses a multilevel hydrodynamic model to reproduce the tidal current field and an advection-diffusion model with bottom boundary conditions for erosion and deposition to estimate transport of fine sediment. Data from the field measurements indicate that the erosion and transport of fine sediments are mainly controlled by tidal current. The sediment transport model reproduces the variation of suspended sediment concentrations during neap-spring tidal cycles reasonably well, and the simulated results also reproduce the observed anti-clockwise residual transport pattern.