To provide a thermal control system and a power generation system in high temperature difference environment, in which safety is high and energy consumption is small.

In the landing machine 1, a capillary pipe driving type two-phase fluid loop 20 as a circulation type thermal transportation fluid loop is included. An evaporator 21 is provided on a side of various instruments 30 forming an object of thermal control, and an evaporator 22 is installed at depth of several tens of cm of underground forming a constant temperature environment. The evaporators 21, 22 use a porous wick material and involve liquid reservoirs 21a, 22a, respectively. The evaporators 21, 22 using the porous wick material also act as a condenser, and are operated so as to condense the fluid evaporated and release heat.