Coil bobbin, coil component and switching power source apparatus

To improve insulating properties of a coil winding having three turns. In a coil bobbin, insulation between mutually adjacent winding members of a first coil winding are achieved by a projecting section. Furthermore, the first coil winding and the second coil winding are insulated from each other by the flange section. Moreover, the projecting sections and the projecting sections are respectively provided in positions at either end when the first coil winding and the second coil winding are viewed in a direction perpendicular to the direction of the axis line. Consequently, even with coil windings having three turns, insulation between the windings is achieved by means of this coil bobbin, and furthermore, insulation is also achieved in the region outside the coil windings as viewed in a direction perpendicular to the axis line direction, thereby making it possible to improve the insulating properties without increasing the number of parts.