Effect of thickness on grain growth in Copper electrodeposits by cyclic stressing was studied by metallographic observation. The thickness of the film was 1µm to 20µm and the number of stress cycles was 3 × 106. Recrystallization by annealing in the films was also examined for comparison. The results show that the nucleation of the grains by cyclic stressing decreases significantly with decreasing thickness, while the grain growth rate is almost independent of thickness. The recrystallized grain size by annealing decreases with decreasing film thickness and is always smaller than the film thickness. The difference in the structural change by cyclic stressing and by annealing is discussed. When the crystal growth caused by cyclic stressing is used as a strain analysis method, the optimum thickness of the deposits is about 10µm.