Coastal eupseongs, which are mainly built in the period of late Goryeo and early Joseon period, are essential materials in studying the history of Joseon period eupseongs. The purpose of this study is to connect the annexation of local districts with the relocation of local government office, so as to categorize the types of coastal-eupseongs and examine the background of their constructions and relocations. Coastal eupseongs are mainly divided into 'maintenance type' and 'Mergence type' according to the annexation of local districts, and maintenance type is broken down into fortress type and non-fortress type in accordance with the existence of old eupseongs(fortresses). Coastal eupseongs can also be categorized into 'application type' and 'relocation type' depending on whether ex-local government offices were reutilized or relocated. Maintenance type is 'fortress-application type'(Gimhae·Gosung·Old Ulsan-eupseong), 'non-fortress-application type'(New Ulsan-eupseong), 'fortress-relocation type'(Dongrae․Kijang․Geojegohyunseong․ Ulsan(Jwabyeongyoung)-eupseong), 'non-fortress-relocation type'(Sacheon․ Hadong·Jinhae-eupseong·Geojesadeongseong) are differentiated by type. Mergence type is divided into 'Merger of Villages after Castle Relocation Type(Changwon·Namhae·Gonyang-eupseong)', 'Merger of Villages before Castle Relacation Type(Ungcheon-eupseong)'. Coastal-eupseongs are moved to other places in need of more affluent water supply(Gimhae·Gijang-eupseong) and wider usable area(Namhae·Gohyunseong-eupseong). Eupseongs were enlarged owing to the population growth, caused by annexations of local districts.(Ungcheon-eupseong) 'Seonso'(navy yard) is a unique feature which cannot be seen in inland eupseongs.