PURPOSE: To divide a perforated structure into a mesh of a quadrilateral, and a mesh of a hexahedron, in the case of a perforated shell block, and a perforated plate block, respectively only by inputting a perforated shape block for surrounding a round hole.

CONSTITUTION: When perforated block information for defining a perforated structure is inputted from a block information input part 11, a block converting part 12 converts and generates a three-dimensional shape block which can execute a mesh division by an intrinsic shape function, for instance, four quadrilateral blocks for surrounding radially a round hole in the case of a perforated shell block, and four hexahedron blocks for surrounding radially the round hole in the case of a perforated plate block, from its perforated block. A separate block mesh dividing part 13 divides this quadrilateral block or hexahedron block by a quadrilateral mesh or a hexahedron mesh. If a mirror image, rotation and translation movement copy instruction is given, a mesh division by a copy processing of a copy processing part 17 is executed.