Abstract : Performance of the asymmetric trapezoidal fin with various upper lateral surface slopes is investigated by using the two-dimensional analytic method. For a fin base boundary condition, convection from the inner fluid to the inner wall, conduction from the inner wall to the fin base and conduction through the fin base are considered. Heat loss and fin efficiency are represented as a function of the fin base thickness, base height, inner fluid convection charac-teristic number, fin tip length and fin shape factor. One of the results shows that heat loss increases while fin efficiency decreases as the fin shape factor increases. Key words : Performance(성능), Trapezoidal fin( 사다리꼴 핀), Fin tip length(핀 끝 길이), Convection characteristic number(대류특성계수), Fin base thickness(핀 바닥 두께), Fin shape factor(핀 형상계수) Nomenclature 1) A : fin surface area, m 2 h : ambient heat transfer coefficient, W/m 2 ・°Ch f : inner fluid heat transfer coefficient, W/m 2 ・°Ck : thermal conductivity, W/m・°Cl