A structure utilizing geothermal energy capable of effectively utilizing a thermal energy in an underground constant temperature layer while using a supplementary heater and an air conditioner and natural energies such as solar heat or solar light, wind power, and water power in order to prevent limited fossil energies such as petroleum, gases, and coal from being exhausted, wherein an insulating wall (A) formed of a plurality of insulation panels (1) connected to each other and extending from a ground surface (4) to the underground constant temperature layer (21) is buried in the ground while surrounding a building (22) adhesively to the ground exposed portion and the underground buried portion of a foundation (5).