To provide a construction method of a foundation for an elevator shaft making excavation construction to the minimum, making most of construction to safe ground work, shortening the time necessary for completion at a high dimensional accuracy and making trouble of residents minimum.

PC foundation 1 made of reinforced concrete manufactured in a factory is subjected to caisson at an installation place of an elevator shaft to construct a foundation. A steel pipe pile 3 is driven at a necessary position and an installation place is excavated in shallow to form a preceding excavated ground 4. A rectangular frame 5 made of steel is horizontally arranged and a preceding concrete 6 is placed on an outer periphery of the rectangular frame. The PC foundation 1 is arranged, a guide member 8 is installed on the rectangular frame and caisson is performed by inner excavation of the PC foundation 1. A beam material 11 is laid on a steel column head 2 of the PC foundation, a hydraulic jack 12 is inserted and a level of the steel column head 11 is positioned meeting a design value. The guide member 8 is removed and a reinforced concrete is placed on a foundation bottom board 14 in the PC foundation 1 to form a pressure-resistance board 15. After securing strength of the pressure-resistance board 15, the beam material 11 and the hydraulic jack 12 are removed and the periphery of the PC foundation is re-buried to accomplish the foundation.

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