A tree system diagram output method of correlating a plurality of objects and outputting the plurality of objects as a tree system diagram includes the steps of: (a) storing, in a first storing part, an identifier specific to each of the plurality of objects written on a first worksheet; (b) selecting at least one object among the plurality of objects written on the first worksheet; (c) pasting the object selected in the step (b) to a second worksheet; and (d) changing the identifier of the object to be pasted in the step (c) to a second identifier.