Navigation system

A navigation system accurately detects a current position at high speed while executing a position correction by a map matching process. When the moving vehicle is positioned near a road branch point, a position on a road existing at a position that is the closest to a presumed current position obtained by a dead-reckoning navigation among roads existing in the first area around the presumed current position as a center is determined to be the current position. When, conversely, the moving vehicle is at a position away from the road branch point, a position on a road existing at a position that is the closest to the presumed current position among roads existing in a second area smaller than the first area is determined to be the current position.