By introducing the idea of the effective stirring length of bubbles, the following equation of nucleate boiling heat transfer was derived and it was shown that the equation had good agreement with the experimental results. [numerical formula] (laminar flow), [numerical formula] (turbulent flow), where [numerical formula] cp=specific heat of liquid, γ' and γ=specific weight of liquid and vapour, λ=thermal conductivity of liquid, σ=surface tension of liquid, γ=latent heat, R=the representative length of heating surface, q=heat flux, α=coefficient of heat transfer, M=900 m-1 and P=1.699 kcal/h. The average line of many experimental results could be represented by the following correlating equation. [numerical formula].