This study experimentally investigated the heat transfer characteristics of a fin with built-in closed-loop self-oscillating heat pipe. The fin part of the test plate consists of small closed-loop channel. The effects of temperature of fin base, channel structure of heat pipe and fin thickness are investigated. The result revealed that the fin efficiency was affected by the base temperature in the case of fin with built-in heat pipe. The fin with meander channel structure case showed higher fin efficiency by increasing channel cross sectional area. On the other hand, the fin with pool channel structure case showed the lower fin efficiency. Moreover, the thinner fin case decreased the fin efficiency due to its higher flow resistance.