To provide a means predicting the vehicle travel state from electrical signals provided by a vehicle manufacture and a means displaying the vehicle travel state of succeeding vehicle based on this information, with herself being handily installed by a buyer himself without requiring difficult work.

This vehicle travel state display device 1 receives the output of the gear shift state detecting sensor S of an engine control box E and transfers the information for identifying the gear shaft state to a on-chip microcomputer 5. A control program for controlling a display device 7 is stored in the microcomputer 5. When the action level of an accelerator pedal is to be displayed, the pedal position is displayed based on the output of a gas flow sensor F and the output of the gear shift state detecting sensor S. The action level of a brake pedal can be predicted and displayed based on the output of the gas flow sensor F and the electrical signal inputted from a speed meter.