A coordinate input apparatus (editor) of a copying apparatus and the like includes: a tablet to output a signal indicative of a position which is arbitrarily designated; a pointing device to designate an arbitrary point on the tablet; a recognizing circuit to recognize the positions in the X and Y directions of the point designated by the pointing device; a data memory to store the positions of the designated point; a controller which, when a special area on the tablet is designated by the pointing device, allows the signal indicative of the special area to be output; and a correcting circuit to correct the range of the special area. The positions of the designated point in the X and Y directions are detected a plurality of times and compared. The input coordinate data is discriminated by the result of the comparison to see if it is valid or invalid. When the input data is valid, a copying operation is performed. When it is invalid, the copying operation is stopped and the fact that the input data is improper is displayed by an LED indicator and a buzzer is activated. With this apparatus, the coordinate data can be accurately input from the editor and also the accurate trimming or masking of the image can be realized without an erroneous input operation.