PURPOSE: To attain to enhance the accuracy of positional detection, by providing a distance sensor and an azimuth sensor to a primary machine present at a reference point and the secondary machine of a running unit.

CONSTITUTION: A primary machine 5 is constituted by providing a turntable 8 equipped with a rotary driving mechanism and an encoder 12 for detecting the rotary angle thereof on a base 7 supported by and moved on a reference track 4 while providing a limit switch 13 for detecting the direction of the primary machine itself to said base 7. A secondary machine 6 is constituted by providing a table 19 equipped with a rotary driving mechanism on a base 18 while providing a light emitter 24 constituting an azimuth sensor along with the light receiver 15 of the primary machine 5 on said table 19. In addition, a mirror 30 equipped with a high speed rotary mechanism and a sonic receiver 31 constituting a distance sensor along with the sonic generator 16 of the primary machine 5 are provided to the top part of the light emitter 24. Now, a rotary angle at a moment, when the light receiver 15 on the table 8 rotating at a low speed is opposed to the mirror 30 of the light emitter 24 rotating at a high speed, is detected by the encoder 12 to calculate the direction of the secondary machine 6 while the opposed distance between the primary machine and the secondary machine is detected from the sonic wave transmitting time from the sonic wave generator 16 to a sonic wave receiver 31.