PURPOSE: To make an item display easy to see in waveforms at display positions by judging respective states when waveforms to be displayed at the same time are crowded or as to waveforms which vary greatly in the Y-axial direction and adding a character display or suppressing it.

CONSTITUTION: The simultaneous display system 10 for plural waveforms which displays numerical data and displays plural waveforms on a display device at the same time and adds characters to the waveforms at equal intervals for columns provided at specific intervals on the X-axial segment is equipped with a means 11 which changes the display columns, waveform by waveform, a means 12 which adds characters as to signals which vary greatly in the X- axial direction as compared with variation in the Y-axial direction, and a means 13 which suppresses the character display when the waveforms are crowded at the character display positions. In this case, the character display position changes, waveform by waveform, in the order of the columns.