PURPOSE: A top down construction method of a core unit of a building is provided to reduce construction costs by reducing the size of a mold support structure and increasing basement construction speed. CONSTITUTION: A top down construction method comprises as follows. The excavation is successively performed, and a steel column (101) for a vertical core is used to construct a lower support wall forming a part of a concrete wall corresponding to a core unit in each basement. An upper core wall is integrated to the upper part of the lower support wall.
