PURPOSE: To eliminate the need to generate a line kind conversion correspondence table, to reduce the load on an operator, and to improve the accuracy of the conversion of line kind data by recognizing the pattern of the line kind data of a conversion source CAD system and collating it with the line kind data of a conversion destination CAD system.

CONSTITUTION: The pattern of the line kind data 3 of the conversion source CAD 1 is recognized and collated with the pattern of the line kind data 13 for the conversion destination CAD 11 stored in a line kind data storage means 7. Then the line kind data 13 for the conversion destination CAD 11 which is the most similar to the line kind data 3 of the conversion source CAD 1 which is recognized by the collation is retrieved. Consequently, the operation for generating the line kind conversion correspondence table for the conversion of the line kind data between the CADs is not necessary, the load on the operator is lightened, and the conversion accuracy of the line kind data is improved.