A method is provided for verifying insulation distances within electrical systems without producing actual system prototypes. A bounding box tree of each component is produced, and root node pairs are put into a queue. The distance between boxes corresponding to two nodes of the root node pair is calculated. If the distance is greater than a predetermined value, no further process is performed for this root node pair, however, if the distance is less than the predetermined value, triangular patches contained in the respective nodes are extracted, and the exact distance between the two triangular patches is calculated. If the resultant distance is less than the predetermined value, the patches are determined to be adjacent to each other. The shortest path along surfaces of components is determined via the above-described process, and verification in terms of insulation is performed on the basis of the determined shortest path.