To intuitively, visually, easily and efficiently prepare a detailing drawing for showing the connection and fitting state of members or the like.

This system is provided with a drawing edit means for editing an arbitrary basic drawing called from a standard working drawing data group by cutting and pasting edit and a storage means storing CAD support data for supporting the preparation of a working plan, the CAD support data has a standard construction drawing data group composed of the set of model basic drawing data modeled for every kind of structure of a building on the basis of an existent working drawing, structure element data set group composed of the set of drawing data classifying a structure for forming the opening part of a structure for each part so that the picture data of the same part concerning the structure of different dimensions with prescribed pitches can be classified for every kind of the relevant structure and can belong to a drawing data set for every part, and a common member data group composed of the set of drawing data of common members of different dimensions at prescribed dimension intervals concerning the common members to be commonly used between the structures of different kinds, and the desired working drawing is prepared by performing the cutting and pasting edit utilizing the drawing data on the arbitrary called basic drawing.