In the present study, a theoretical analysis for the laminar film condensation in a finned vertical rectangular channel is carried out to clarify the heat transfer characteristics of plate-fin condensers. In the analysis the following assumptions are employed. The bulk vapor is pure and saturated, and the effect of viscous shear of vapor on the liquid film is negligible. The heat conduction in the fin is one-dimensional, and the base surface temperature is a constant. The local characteristics of liquid film shape and fin temperature are examined, and a heat transfer correlation including the effects of fin shape parameters is proposed.