A method, for manufacturing a device for canceling an undesirable magnetic field around an on-line electric vehicle, the method comprising, calculating a primary magnetic field generated by a current flowing through a power line, calculating a first undesirable magnetic field, calculating a second undesirable magnetic field, obtaining an entire undesirable magnetic field by calculating a vector sum of the first and second undesirable magnetic fields, obtaining a number of turns of a coil to be wound around one end or both ends of the power acquisition device which maximally cancels the entire undesirable magnetic field, and winding the coil around the end or ends of the power acquisition device in accordance with the obtained number of turns, and short-circuiting each coil.