PURPOSE: To process redrawing by a pencil in a relatively short time by storing drawing coordinates of the pencil and retrying drawing by the pencil back from the eraser use point of an opposite person.

CONSTITUTION: When an eraser is used, the input from a handwriting input device 10 and an input which is received are processed in order. When the pencil is used, writing is re-executed by the reception of erasure. At this time, writing which is performed between erasure and next erasure includes writing which is performed on a terminal by using the eraser and never re-executed by being traced back more than a writing process performed on the terminal where the eraser is used. On the terminal where the pencil is used, writing following the writing processed on the terminal where the eraser is used is also performed between the erasure and next erasure, but this becomes an object of redrawing in 2nd or succeeding erasure.