A magnetic field probe apparatus includes a loop-like conductor and feeder lines spaced at a distance from the loop-like conductor. The shape of the loop-like conductor and the arrangement of the feeder lines are adjusted in such a manner that the resonance frequency determined by the combination of the inductance of the loop-like conductor line and the capacitance formed between the looped-conductor and the feeder lines, is matched to the frequency of the magnetic field generated by and in the vicinity of a measurement object (e.g. electronic device) or the frequency of the electric signal which generates the magnetic field. With the magnetic field probe apparatus according to this invention, the magnetic field in the vicinity of the measurement object can be measured with high sensitivity.