PURPOSE: To facilitate fine control of the inductance of a solenoid coil by a method wherein a conductor film formed on the surface of a wound core is cut spirally with set number of turns, width and pitch in order to from a coil.

CONSTITUTION: The surface of a bobbin 1, which is formed in a cylindrical form and consists of an insulative magnetic material, such as a ferrite, is covered with a paste and the paste is fired in an electric furnace to form a conductor film 2. Then, this film 2 is cut in such a way that a spiral cut groove 3 is formed and a coil 4 is formed on the residual part of the film 2. The electrical characteristics, such as an inductance, of a solenoid coil are set by the number of turns, width, pitch or the like of the coil 4. Here, it is possible to execute a cutting work on both ends of the solenoid coil while the inductance fixed on an inductance measuring terminal is measured during the formation of the coil 4 using the groove 3 and the fine control of the inductance can easily be executed.