Two and six-layer stack accumulative roll bonding (ARB) processes were applied to commercial purity aluminum in order to investigate the effect of the stacking layer number on the mechanical properties. The initial thickness of the aluminum sheets for two and six-layer stack ARB was 1mm and 0.5mm, respectively. Two-layer stack ARB was performed by 50% reduction per cycle. For six-layer stack ARB, the six aluminum sheets were first stacked together and cold-roll-bonded by 50% reduction rolling, and then followed by four-pass rolling so that the final thickness was 0.5mm. The sheet was then cut to the six pieces of same length and the same procedure was repeated to the sheets. The tensile strength of the ARB processed specimens increases with the number of ARB cycles in both two and six layer stack ARB. The tensile strength is lower by the six-layer stack ARB than that by the two-layer stack ARB. The elongation slightly decreases with the number of the ARB cycles, regardless of the stacking layer number. TEM observation reveals that the grain size of the six-layer stack ARB is larger than that of the two-layer stack ARB. The effects of the number of the layers in stacking are explained by the redundant shear defomation.