Two principal donor bound-exciton (BE) lines with a linewidth of 0.6 meV at 4.2 K have been observed in both the not intentionally doped homoepitaxial GaN layer and the hydride vapor phase (HVPE) grown epitaxial lateral overgrowth (ELO) GaN layer. When the external magnetic field was applied perpendicular to c-axis up to 8 T, each BE line splits into two components due to the Zeeman effects. The localization center, which binds exciton, is related to a simple donor impurity. From the observed two-electron satellite peaks, the related donor levels are estimated to be about 25.1 and 31.5 meV, which are smaller than the effective mass donor binding energy.