To provide a navigation system ensuring highly accurate positioning even when a satellite radio wave subjected to multipath noise is received.

A satellite navigation processing section 104 finds the vehicle speed from the Doppler shift of a received satellite radio wave and delivers the vehicle speed to a display processing section 112. An estimation navigation processing section 19 finds the vehicle speed from the revolutions or the like, of the wheel and delivers the vehicle speed determined to the display processing section 112. When the difference between these speeds exceeds a preset reference level, the display processing section 112 determines that a satellite radio wave subjected to multipath noise is employed in the positioning operation and issues a command to the satellite navigation processing section 104. The satellite navigation processing section 104 finds the current position by rearranging the satellite radio waves being employed in the positioning operation thus ensuring highly accurate positioning.