PURPOSE: To invite a driver's attention to a safe drive by showing that a curve exists.

CONSTITUTION: A travel track calculation means 102 computes the travel track of a vehicle on the basis of the travel speed and direction thereof detected with a vehicle sensor 101. Also, an estimation means 103 estimates the current position of the vehicle on the basis of a travel track and map data 100 detected with the means 102. Furthermore, a display means 103 shows the current position of the vehicle estimated with the means 103 and map data 100 containing the current position. The map data 100 contains the curvature of a road, and a curve judgement means 105 judges that a curve exists, on the basis of the curvature of a road existing in a travel direction and detected with the vehicle sensor 101. Also, a reporting means 106 reports that a curve exists, when the existence thereof is identified with the means 105.