PURPOSE: To provide a highly reliable composite coil component for miniaturizing a power supply circuit inexpensively by constituting a transformer for current detection and a smoothing coil on a same core.

CONSTITUTION: C-shaped or U-shaped thin silicon steel plates having a magnetic gap, are laminated and the winding part is encased in an insulating case 2 being split by means of a partition flange 7 thus producing a composite coil component. A winding 4a for smoothing coil is wound around one spool part of a core and a winding 4b for current detection is wound around the other spool part of core in the same direction as the winding for smoothing coil.