To provide an apparatus which enables recovery and reuse of a weight used for placing a heat exchange tube in a precast pile, and can set the heat exchange tube at a designated depth in the precast pile.

An apparatus of this invention inserts a heat exchange tube 10 for underground heat usage into a precast pile 14, against buoyancy force acting on the tube, and sets it there. The apparatus comprises: a fitting ring 20 in which the heat exchange tube 10 is attached on its inner periphery; a pushing gear which is loaded on the fitting ring 20 in a removable and recoverable manner to push down the fitting ring during the insertion of the heat exchange tube 10 into the precast pile; and holding means 21 and 25 which hold the fitting ring 20 inserted into the precast pile on the inner periphery of the precast pile 14.