Disclosed herein is an ELF or LF magnetic field measuring system, which can easily measure each magnetic field component existing in a free space generated by electric appliances or in a human body phantom filled with a specific fluid. A 3-axes magnetic field probe for use in the magnetic field measuring system comprises resistive lines in a protective sleeve rod electrically connected to the transmission board, an isotropic sensing head having a cubic shape, one end of the protective sleeve rod being rigidly connected to a corner point of the cubic sensing head where three faces coincide, and three bobbins adhered to three adjacent faces which coincide at a corner point diagonally opposite to the first corner point. A coil is wound on the periphery of each of the bobbins.The sensor is moved by an automatic mechanical machine to scan a pre-programmed surface where the magnetic field distribution is to the evaluated.