In revising a figure element, the figure element (C.sub.2) to be revised is designated, the designated figure element (C.sub.2 ) is displayed by a type of line or and color different from those of other figure elements, the figure elements (S.sub.1, C.sub.1) used in defining the designated figure element (C.sub.2) are displayed by a line of a different type and color, a message (M) which includes definition statements of the figure elements (S.sub.1, C.sub.1), as well as a radius necessary for defining the figure element (C.sub.2), is displayed on a display screen, and revision of the figure element is executed by referring to the display.