A coil device includes a winding core, a wire, and a terminal fitting. The winding core is made of a magnetic material and includes a flange. The wire is wound around the winding core. The terminal fitting is attached to a part of an outer surface of the flange. The terminal fitting includes a contact part and a protrusion plate part. The contact part is contacted with the outer surface of the flange. The protrusion plate part is formed integrally with the contact part and protrudes away from the flange. The protrusion plate part includes a wire connection surface and a main mounting surface. A lead end of the wire is connected to the wire connection surface. The main mounting surface is located opposite to the wire connection surface and is connectable to an external circuit.