The results of optical studies of the effect of pulsed magnetic field (B = 60 mT, τ = 1.2 ms, t = 5 min) on the structural perfection and recombination properties of epitaxial GaN films grown on sapphire are presented. Nonmonotonic changes in the spectral dependence of transmittance and photoluminescence were detected for GaN films after exposure to magnetic field. They occurred during several days, with a maximum deviation from the initial values on the 12th day. The observed effect is presumably related to the magnetic field-induced changes in parameters of the surfaces and interfaces of epitaxial films.