The present invention provides a relative position and/or posture measuring system for measuring relative positions and relative postures between a magnetic field generator and a magnetic field detector by detecting a change in a magnetic field, in which the magnetic field generator includes a clock generator, a plurality of M-sequential code generators, a plurality of spread code generators, a plurality of integrators, and a voltage to current converter, and transmission coils TX, TY, TZ generate magnetic fields according to driving currents based on spread code obtained by converting code sequences generated by the M-sequential code generators to spread code with the spread code generators. The magnetic field detector reversely spreads received magnetic field detection values to obtain a magnetic field amplitude, and computes relative positions and relative postures of the two from the magnetic field amplitude.