By a rotating disk method which had quantitatively been treated in fluid motion, silicon epitaxial deposition using the system was effected at various susceptor rotation speeds and various pressures. Calculation of the growth rate was initially made with a one‐dimensional model of an infinite diameter disk without considering natural convection caused by local heating. This was followed by a numerical solution of Navier‐Stokes equations, continuity equation, and equation of energy of cylindrical coordinates, using a three‐dimensional model and taking natural convection into consideration. With the three‐dimensional model including natural convection, a quantitative description can be given of the influence of susceptor rotation speed and pressure on the growth rate at a temperature higher than 1150°C.