Numerical analysis was carried out to clarify melt convection of LiNbO3 in a double-crucible Czochralski process using the accelerated crucible rotation technique. We investigated the effects of window shape of an inner crucible on melt convection in a double crucible. It was found that the height of windows of an inner crucible has a large effect in comparison with the effect of width of windows on melt convection. When the window height was set high, melt in the outer crucible could easily flow into the inner crucible. Then it effectively modified heat transfer near the melt-crystal interface. On the other band, when the window height was set low, cell formation was observed near the melt-crystal interface. (C) 2004 Elsevier B.V. All rights reserved.