After the Building of Catholic Diocese of Gwangju was established in 1937, this Building of Catholic Diocese of Mokpo was used as the first base for missionary works in the Gwangju, Jeollanam-do, and Jeju areas. The building displays a symmetrical structure with a semicircular arch and a porch with a pilaster at the center. A horizontal white band runs around the building below the eave and between the floors, while vertical windows are repeatedly arranged on the walls. The original features of the building’s interior, including the wooden stairs, finishing plaster on the ceiling, and sliding doors, have been well preserved. In 1956, the building of Catholic Diocese moved to a new location in Gwangju, and the building came to be used as the Mokpo Branch of the Missionary Sisters of St. Columban, St. Columban Hospital, and Seongsin Women’s College of Nursing. It provides invaluable materials about the early history of the Catholic Diocese of Gwangju and the medical missionary works of the Missionary Sisters of St. Columban.