The strain analysis of a GaN epilayer with different growth times on a c-plane sapphire substrate via a two-step growth method, using low-pressure, metalorganic chemical vapor deposition, was conducted based on the precise measurement of the lattice parameters, using high-resolution X-ray diffraction. The high-temperature growth time was changed at a fixed growth condition. The c- and a-lattice parameters were measured, followed by the out-of-plane and in-plane strains. Then, the biaxial and hydrostatic components were extracted from the total strain values obtained, and were discussed in this paper as functions of GaN growth time.