Transient changes in surface morphologies of Ag-Sb thin films electrodeposited from an aqueous electrolyte have been studied. Measurements of the potential and current density applied during electrodeposition reveal that stripe patterns that comprise bright and dark regions are formed within a small range of the potential and current density that exhibits no oscillatory behavior. In addition, the experimental results on the transient current density are found to be in good agreement with the solutions of unsteady diffusion equations, whose results give the ratios of the kinetic constants to the diffusion coefficient that may be related to a necessary condition for the Turing instability in reaction-diffusion systems. Fourier analysis of the time-series stripe images shows that stripe spacings change with the area ratio of the bright regions to the dark regions fixed. This indicates that the stripe patterns formed at the different deposition times emerge on different length-scales.