PURPOSE: To execute the automatic wiring in which a path detection rate is high and a memory is used efficiently by preparing plural prescribed procedures, executing a search of high linearity and a flexible alternative search, and also, containing a path by a data structure of a binary tree node.

CONSTITUTION: A procedure for executing a linear search from a source point and recording a coordinate of its point to a binary tree node at the time when an obstacle is detected, a procedure for searching an alternative route of the obstacle and detecting an alternative point, a procedure for executing a linear search and calculating a point coordinate at the time of reaching the next obstacle or a target line, a procedure for adding a binary tree node to this point and recording a coordinate of the point and a relation to the existing binary tree node, a procedure for back-tracing the data of the existing binary tree node at the time of reaching a new fault in an alternative point detecting process and changing a tree structure, a procedure for starting from an arrival point and executing recursively and repeatedly the second - fifth procedures until the time when the alternative search is ended, and a procedure for selecting an optimal path at the time when the alternative search is ended are provided and executed.