Excessive heat and the resulted perspiration within a prosthetic socket were the most common causes for reporting a reduced quality of life for prosthesis users. This paper presents a novel thermal management device to maintain a constant skin temperature for a lower-limb prosthesis. To decrease the prosthetic socket's thermal resistance, heat pipes were used to concentrate heat flux from the simulated skin surface to a cooling region on the outer surface of the socket where a compact heat sink was attached. A small fan was used to convect heat from the heat sink to the ambient surroundings. Thermal resistance of the cooling device was adjusted to match various thermal loads by changing the fan power. Experiments showed that cooling capacity of the prototype device ranges from 2.1 W to 7.0 W at an ambient temperature of 23.0 °C. The automatic control mode to maintain a constant skin temperature was also demonstrated. Further analysis showed that the device can potentially maintain a constant skin temperature for a thermal load as large as 9.4 W. The compact size, quiet operation and heat removal capability make the device suitable for maintaining a comfortable and healthy thermal environment inside the prosthesis socket.