This thesis describes a system which extracts the circuit information from MOS/LSI mask artwork geometry. The recognizable circuit elements are polysilicon gate MOS transistors. The output format of circuit information extracted by the system is the same as SPICE2 input syntax. We have developed an algorithm solving the "rectangle intersection reporting" problem, which is the most important one to be solved to realize efficient circuit extracting system. The worst case time complexity of our algorithm is O(nlogn + K), space complexity O(n), where n is the number of rectangles and K is the number of intersecting pairs. It also solves the rectangle enclosure problem which is not solved by the known edge-based algorithms.