To provide a method and device for constructing a foundation having heat exchange function using ground water in soft ground in which the burying of a heat exchange system is simultaneously performed with the laying of a ground reinforcing means such as burying of pile which is indispensable in the construction of a building on soft ground by use of ground water or underground bed having substantially a constant temperature throughout the year.

This method for constructing the foundation having heat exchange function using ground water in soft ground comprises injecting water while excavating a vertical hole in the soft ground to substitute excavated sediment sludge with the water; inserting a cage-like reinforcement having a conduit for circulating a heat exchange medium for air conditioning equipment wound around the circumference to the excavated vertical hole; injecting fresh concrete adjusted in pH and adjusted with hardener thereto to form a foundation pile; and connecting both ends of the conduit for circulating the heat exchange medium to the heat exchange medium circuit of the air conditioning equipment.