Provided is a geothermal heat system having reduced heat source residual heat of a geothermal heat pump. The geothermal heat system includes a ground heat exchanger unit, a geothermal heat pump, and a residual heat storage tank. A portion of heat source residual heat remaining in the geothermal heat pump is transferred on a geothermal heat exchange medium passing through the geothermal heat pump so as to be stored in the residual heat storage tank. As the internal temperature of the residual heat storage tank gradually becomes the same as the temperature of the underground, the thermal load of the underground is removed. At least a portion of the heat source residual heat produced during provision of cooling/heating to the location of use is processed, thereby improving the operating efficiency of the geothermal heat system having reduced heat source residual heat of a geothermal heat pump.