We investigated theoretically the distribution of lattice distortion in three dimension around self-assembled InGaAs/GaAs quantum dot (QD) and its influence on vertical QD stacking. Based on the finite element method, we computed the strain distribution around pyramidal QD so that the total strain energy takes the minimal value. Mechanism of QD alignment in growth direction is discussed taking into account the effect of indium hole formed in stacked wetting layer just above underlying QD. Assuming that the QD in the stacked layer is grown at the position where the lattice distortion is minimal, we estimated the critical thickness of spacer layer between QD layers to make QDs align in growth direction, that agrees well with previously reported values in experiments. (c) 2006 Elsevier B.V. All rights reserved.