The endothermic reaction and heat transfer characteristics of a platinum-catalyst-coated fin which undergoes a methanol decomposition reaction are investigated experimentally. Fin base temperature is varied widely over the range of practical interest. The local temperature along the fin structure and the evolution rate of decomposed gas measured agree well with those predicted by the analytical model described in the previous paper (Reaction and Heat Transfer Characteristics of Catalyst-Coated Fins (Theoretical Analysis of Fins with an Endothermic Reaction), JSME Int. J., Ser. B, Vol. 42, No. 2 (1999), p. 255). For the ranges of dimensionless parameters examined, the effects of the mass transfer of reactant species from bulk fluid onto the fin surface and the heat absorption by the reaction on fin efficiencies of the reaction rate and heat transfer are shown to be negligible. From theoretical consideration, for the case in which the reaction rate on the fin surface is not affected by the mass transfer onto the fin surface and the heat absorption by reaction in general, one dimensionless quantity, which is expressed as a function of dimensionless parameters, is shown to be dominant for fin efficiency of the reaction rate in the ranges of dimensionless parameters which are practically possible. The simple approximation of the fin efficiency of the reaction rate expressed in terms of the dominant dimensionless quantity well predicts the results obtained by the experiment.