PURPOSE: To attain high-precision position detection with lines and detection parts both reduced in number by sending an electromagnetic wave signal to not less than two transmission media differing in transmission rate and by measuring relative transmission time delay generated on each transmission medium between the transmission point and reception point.

CONSTITUTION: Two induction radio open lines 1 and 2 are laid along the track of traveling body 3 a signal from signal supply 4, provided to traveling body 3, generating an electromagnetic wave signal of approximately 10KHz to 1GHz is transmitted to lines 1 and 2 through antenna 11 and 12. The above-mentioned signals transmitted through lines 1 and 2 are received by receivers 31 and 32 and led to phase difference detector 5 to detect the phase difference, and on the basis of the difference, the position is displayed by position display unit 6. In addition, terminating resistances 21 and 22 are connected to terminals of lines 1 and 2. Line 1 is a delay line composed of parallel lines using helical lines of structure (a) and line 2 is a delay line composed of straight-line type parallel lines like (b).