On March 11, 2011, the Great Tsunami hit the northeast Japan's coasts, causing severe disaster along the coastline. The river mouth bar of the Same River flowing into a pocket beach with 6.5 km length bounded by Point Ryugu and Nakoso fishing port on the north and south ends, respectively, was eroded and disappeared by the return currents of tsunami. Simultaneously ground subsidence by 0.5 m occurred due to the earthquake in this area. In this study, the shoreline changes of this pocket beach after the tsunami and ground subsidence were investigated using aerial photographs and bathymetric survey data. It was found that the recovery of the river mouth bar caused beach erosion on the nearby coasts.