Impurity effects of tri-valent cations on the growth of (1 1 1) and (1 1 0) faces of SnO2 in the SnO2-Cu-2O flux system were investigated using an improved dipping method by which supersaturation can be maintained constant, using Cr3+ as a representative cation. It was confirmed that the presence of Cr3+ accelerates the growth rate in the < 1 1 1 > direction and suppresses that in the <1 1 0 > direction. Observation of the surface morphology of the (1 1 0) face indicated that Cr3+ inactivates kink sites of <0 1 > steps on the (1 1 0) surface, and breaks periodic bond chains on the (I 1 1) surface, resulting in the transformation of the (1 1 1) surface from a smoother to a rougher interface.