To provide a means for further effectively utilizing heat energy of an underground constant temperature layer while supplementally using a heater, an air conditioner and natural energy such as solar heat or the light, wind power and hydraulic power for preventing exhaustion of fossil energy such as limited petroleum, gas and coal.

This structure utilizing geothermal energy is buried by surrounding a building 22 by a thermal insulation wall A extending up to the underground constant temperature layer 21 from a ground surface 4. The thermal insulation wall A is constituted by continuously connecting a plurality of thermal insulation panels 1, and is buried in close contact in an aboveground exposed part and an underground buried part of a foundation 5.