PURPOSE: To flexibly select a travel route and a travel pattern by using a bar code which is formed of a light reflecting body and has coordinates recorded as a mark and using a bar code reader as a mark sensor.

CONSTITUTION: The output dθs/dt of a rate sensor 1 is corrected with a bias error Δdθ/dt outputted by a rate sensor correcting circuit 2. Azimuth acceleration dθ/dt is found and integrated by an integration circuit 4 to obtain an azimuth angle θ. A speed V is calculated from the product of the rotating speed n of a rear wheel 5a and a scale factor A and integrated by a position detecting circuit 8 to obtain a coordinate position. The coordinates of the mark formed on a travel path are recorded as the bar code. Mark sensors Q1-Q7 read the coordinates each time the mark is passed during the travel and an updating circuit 9 calculates the real coordinate position and azimuth. Those coordinate position and azimuth are used as initial values of the integration of the speed V and the integration of the azimuth acceleration dθ/dt. Consequently, a flexible guidance becomes possible.