To provide a rear display device of an automobile, which is capable of notifying a driver in a succeeding vehicle of desired character information with an extremely simple operation.

The rear display device includes: a speech recognition device 12 recognizing voice generated by a driver DR in a cabin; and a transparent conductive film 13 displaying the content of the voice recognized by the speech recognition device 12 in characters. The transparent conductive film 13 is adhered to a lower part of rear window glass 8 in a rear part of the automobile.