1. An input-output coordinate transforming method for an input-integrated display apparatus having a structure in which an input coordinate designating means is physically connected with a screen of a display device and is integrally combined therewith, wherein coordinates inputted through said input coordinate designating means by an operator are subjected to coordinate transformation before being supplied to said display device so as to make an output point on said display coincide with a corresponding input point on said input coordinate designating means when viewed by the operator, comprising the steps of: displaying a plurality of predetermined reference coordinate points on said display screen and inputting through said input coordinate designating means the coordinates of points thereon designated by the operator, said points being designated such that they coincide with said reference coordinate points, respectively, when viewed by the operator; arithmetically determining constants of predetermined coordinate transformation expressions representing correspondence between the input coordinates and the output coordinates on the basis of said plurality of coordinates of said displayed reference coordinate points and said plurality of coordinates of said points designated by the operator; and transforming the input coordinates inputted through said input coordinate designating means into output coordinates which are supplied to said display device by using said coordinate transformation expressions which contain said determined constants.