PURPOSE: To cut an existing pile without breaking thereof so as to be utilized again concerning disassembly process for cutting the existing pile and the foundation building flame in a disassembly work of the concrete foundation part of a building.

CONSTITUTION: When a pile head in a joint part between an existing concrete pile 1 and a foundation building flame 2 is cut, the pile head of the existing pile 1 is bored by moving a core boring machine in the horizontal direction. Cutting thereof is performed by shifting the core boring machine in the radial direction of the existing pile 1.