The eptiaxial growth of Ge on the clean and surfactant (Sn) adsorbed surface of Ge(111) was studied by the intensity oscillation of a RHEED specular spot. In the case of epitaxial growth without the adsorbed surfactant, the RHEED intensity oscillation was stable and periodic up to 24 ML at the substrate temperature of $200^{circ}C$. Therefore the optimum temperature for the epitaxial growth of Ge on clean Ge(111) seems to be $200^{circ}C$. However, in the case of epitaxial growth with the adsorbed surfactant, the irregular oscillations are observed in the early stage of the growth. The RHEED intensity osicillation was very stable and periodic up to 38 ML, and the d2$ imes$2 structure was not charged with continued adsorption of Ge at the substrate temperature of 2002$ imes$2. These results may be explained by the fact that the diffusion length of Ge atoms is increased by decreasing the activation energy of the Ge surface diffusion, resulted by segregation of Sn toward the growing surface.