In the present study, the effect of the condenser section length on the thermal perfor-mance of PHPs was investigated experimentally under the constraint of fixed evaporator section and total lengths. Using MEMS techniques, silicon-based PHPs with 10 turns and hydraulic diameter of 667μm were fabricated to evaluate the thermal performance of sili-con-based PHPs. The evaporator section and the total lengths were fixed at 20 mm and 100 mm, respectively. The thermal resistance was evaluated from temperature measurement while flow visualization was conducted using high speed camera with different condenser section lengths. The optimum condenser section length, for which the temperature of evapo-rator section was the lowest, was found to be 10mm experimentally. When the condenser section length became smaller than the optimum length, the temperature of the evaporator section increased because the heat transfer area of the condenser section decreased. When the condenser section length became larger than the optimum length, the stopover phenom-enon was observed through flow visualization. The stopover phenomenon affected the for-mation of the liquid film in evaporator section and adiabatic section of PHPs. The variations in temperature of the evaporator section with time was less significant as the condenser sec-tion length decreased due to continuous liquid film supply.