An approximate theory, accounted for the effects of both energy convection and fluid acceleration within the film condense layer, is reported in this paper and the similar method (Karman-Pohlhausen's method) to the heat transfer by free convection has been used also for the laminarfilm condensation on a vertical wall. Heat transfer results are expressed by the following simple equations and indicate a good agreement with the numerical exact solutions for special Prandtl numbers, which have been given by Sparrow and Gregg recently. (I) for high Prandtl numbers [numerical formula] (II) for low Prandtl numbers [numerical formula] where β is a functon of Prandtl number and of cΔT/hfg and is given by Figs. 2 and 3. The symbols used in the above equations are as follows : Nux : local Nusselt number, k : thermal conductivity, hfg : latent heat of condensation, c : specific heat, ΔT=Tsat-Tw ; Tsat : saturation temperature, Tw : wall temperature, g : acceleration due to gravity, ν : kinematic viscosity, ρ : condesate density, ρv : vapor density, x : distance measuring along wall from leading edge.