This article reports the results of real-time scanning tunneling microscopy (STM) observation of Au⁺ ion irradiation effects on high-temperature Si surface, which was achieved by our original ion gun and STM combined system. Sequential STM images of a Si(111)-7×7 surface kept at 500^oC were obtained before, during, and after Au⁺ ion irradiation with 3 keV. Vacancy islands, which are two-dimensional clusters of surface vacancies, and 5×2-Au structures were formed on the surface and their size were changed during the subsequent thermal treatment. This method enables us to count exact numbers of vacancies and Au atoms on the surface by measuring the sizes of vacancy islands and 5×2-Au reconstructions. The timescale of the growth of the 5×2-Au domain suggests that the implanted Au atoms diffuse to the surface almost without interacting with point defects induced by the ion irradiation.