Abstract: Provided is a coil component including a core member and a wire wound around the core member, wherein a cross section of the core member perpendicular to a winding axis of the wire wound around the core member has a circumference shape comprising at least three first arcs and connecting lines connecting the at least three first arcs adjacent to each other, and each of the at least three first arcs has a predetermined radius and a predetermined central angle for closely contacting the wire and the core member.

Abstract: A coil device 1 comprises a coil 10, a T-shaped core 20 including a columnar portion 21 around which the coil 10 is disposed and a flange 22 formed at a first end 21a of the columnar portion 21 in an axial direction thereof, and an exterior body 30 covering the coil 10 and the columnar portion 21 and made of an exterior material including magnetic particles and a resin. The core 20 is provided with a recess 40 including at least one of a first recess 41 or a second recess 42. The first recess 41 extends between the first end 21a and a second end 21b of the columnar portion 21 in the axial direction. The second recess 42 extends from an inner side towards an outer side of the flange 22.