The rocking curve of reflection high-energy electron diffraction (RHEED) is widely used to determine surface structures. We have built up a new apparatus of RHEED system with two pairs of magnetic coils to measure accurately the rocking curves in short time. By using this system, we succeeded in the studies of effective surface Debye temperature, dynamic structure change during epitaxial growth of Si/Si(111) and surface structure at high temperature near the melting point, and discovered an additional surface phase on the Si(111) surface. In this review, I report the new apparatus and some results of surface phase transition of the Si(111) surface at high temperatures.