To provide a navigation system which enables a driver to immediately judge the right and the left in an advancing direction in the rear field of view, and to grasp the position and the advancing direction of a vehicle, on the occasion of backward movement of the vehicle.

The navigation system includes an image processing means 8, which performs processing of converting a surrounding map image into an image obtained by rotating it at an angle of 180° when a backward movement detecting means 4 detects that the vehicle moves backward or that the vehicle is in a state of being movable backward and when the surrounding map image displayed on a display means 5 is a plane map image. The means 8 also performs processing of changing the surrounding map image over to a bird's-eye view image obtained by looking down aslant on the side in the rear of the vehicle from the side in front of the vehicle when the surrounding map image displayed on the display means 5 is the bird's-eye view image obtained by looking down aslant on the side in front of the vehicle from the side in the rear of the vehicle.