To provide an on-vehicle navigation system for accurately predicting a lane position during running.

In the on-vehicle navigation system 50 provided with a GPS part 7 and a map information storage part 2, CPU 1 includes a current position calculating part 21, a white line detecting part 22 for detecting a white line from a camera image of a camera 11, a running lane position predicting part 23, and a guide timing control part 24. An operation signal of a winker switch 12 is input to CPU. The running lane position predicting part determines lane modification by a signal from the winker operation signal and a white line detecting part when detecting a running road of an own vehicle, which specifies a lane position during running. The guide timing control part detects a forward branch, and controls so as to perform branch guide to a driver at a position before a prescribed distance on the basis of the specified lane.