To easily acquire the dimensional amount of marking positions based on a CAD drawing.

When an installation requiring a plurality of marking positions is installed in a predetermined construction object, the CAD drawing showing the construction object is displayed on a predetermined screen (S1). A pattern formed of a plurality of specific signals corresponding to the plurality of marking positions are arranged on the displayed CAD drawing (S2). Based on the CAD drawing on which such a pattern is arranged, the dimensional amount of the plurality of marking positions based on a predetermined coordinate reference is determined (S5), a list of the dimensional amount of the marking positions is created (S7), and the list of the dimensional amount is outputted (S8). When a plurality of coordinate references exist, a layer is created every coordinate reference (S3), the specific signals are distributed to respective layers (S4), and the dimensional amount of the marking positions is preferably determined and outputted every layer.