The blood flow regulation of the circle of Willis is thought to have a close correlation with the anatomy of the circle. In this study, we performed the computational fluid dynamics simulation with three-dimensional model in order to consider the relationship between the cerebral blood flow and the geometric configuration of blood vessels. The decrease of blood flow at the left internal carotid artery (LICA) led to the greater reduction of the blood flow at the left middle cerebral artery (LMCA) and the left anterior cerebral artery (LACA) which are near the LICA, and led to the smaller reduction at the left posterior artery (LPCA) and the blood vessels on the right side of the circle which are far from the LICA. Furthermore, the decrease of blood flow at the basilar artery (BA) led to the greater reduction of the blood flow at the left and right PCAs which are near the BA, and led to the smaller reduction at the MCAs and ACAs which are far from the BA. These results indicate that the redistribution of the blood flow in the circle of Willis is affected by the configuration, such as the spatial proximity of the blood vessels.