NOVELTY - The geothermal energy apparatus (1) has a steam pipe (3) that is inserted in a heat-collection hole from a ground surface side (4), and is connected with the heat-collection hole at an airtight state, and accommodates a turbine in airtight state. A liquid tube (11) is provided so that a downstream portion and the heat collection hole of turbine are connected. A working fluid is enclosed with a pipe line currently formed of the heat-collection hole, steam pipe, and liquid tube, so that turbine is driven by working fluid which is heated in the heat-collection hole and evaporated.    USE - Geothermal energy apparatus.    ADVANTAGE - The provided geothermal energy apparatus can reduce the thermal resistance at the time of geothermal heat being transmitted to the working fluid of a liquid phase is provided. Since the heat-collection hole or the underground pipe is formed as some airtight pipe lines in which a working fluid carries out a circulation flow with phase change, the thermal resistance at the time of transmitting heat with respect to a working fluid from rocks can be reduced. Since the heat-collection hole or the underground pipe, and the steam pipe are connected with the airtight state, it can suppress or prevent that the working fluid which carried out phase change to the gaseous phase leaks outside. Thus the quantity of the working fluid for driving a turbine or a generator can be reduced, and a running cost can be reduced. The apparatus can produce electric power with geothermal heat, even when desert moisture contents are few places. The area in which heat is transmitted from rocks can be increased when the heat-collection hole and the underground pipe are radially provided toward hot rocks, so that the working fluid of a liquid phase can be made easier to vaporize, thus the efficiency of geothermal energy apparatus can be improved. The contact area of the heat transfer face which transmits heat to the working fluid of a liquid phase, and the working fluid of a liquid phase can be increased by injecting the working fluid of a liquid phase radially from a liquid tube. Thus the efficiency as a geothermal energy apparatus can be improved.    DESCRIPTION OF DRAWING(S) - The drawing shows the longitudinal sectional view of the illustrating the side structural view of the geothermal energy apparatus.    Geothermal energy apparatus (1)    Steam pipe (3)    Ground surface side (4)    Liquid tube (11)    Sealing segment (13)