1. A positioning device that detects a position of a mobile body with a radio navigation positioning unit, comprising: a first autonomous sensor configured to obtain behavioral information on the mobile body; a position detecting unit configured to obtain an estimated position of the mobile body by updating a detection result from the radio navigation positioning unit based on the behavioral information obtained by the first autonomous sensor; a map data positioning unit configured to refer to a map data storage unit based on the estimated position obtained by the position detecting unit and thereby to obtain a map data linked position that is a predetermined distance away from a link corresponding to the estimated position; and a most probable position estimating unit configured to estimate the position of the mobile body from the estimated position and the map data linked position by using the Kalman filter.