A code positioning part calculates a position of a subject vehicle and a receiver clock based on an orbit of a GNSS satellite in which an error indicated by a positioning reinforcing signal is corrected and a first corrected pseudorange being a pseudorange of the GNSS satellite in which an error indicated by the positioning reinforcing signal is corrected. A receiver clock bias error correction part determines a difference between a two-point range between a position of each of a plurality of GNSS satellites and the position of the subject vehicle and the first corrected pseudorange as an unknown error, and determines a receiver clock bias error of the pseudorange based on the unknown error. A code positioning correction part recalculates the position of the subject vehicle, using a second corrected pseudorange that is obtained by correcting the first corrected pseudorange using the receiver clock bias error.