To provide a road monitoring device for showing a velocity example allowing a vehicle to pass through a monitoring area safely to the driver of the vehicle entering the monitoring area when an obstacle such as a stopping vehicle exists on a road of bad visibility being the monitoring area.

The device is provided with an obstacle position calculation part for calculating the position of the obstacle, a sight distance calculation part for calculating the obstacle sight distance of the curve by the position of the obstacle, a safety upper limit calculation part for obtaining a safety upper limit by this sight distance and a display part for displaying its result.