A coil device includes: a core including a winding core part and a flange part at an axial end part of the winding core part, a coil part including a first wire and a second wire wound around the winding core part, a first terminal electrode, formed on a flange part mounting surface and a lead-out part of the first wire is connected, and a second terminal electrode, formed on the mounting surface of the flange part spaced apart from the first terminal electrode and a lead-out part of the second wire is connected, in which the flange part includes a concave part, recessed from the upper surface of the flange part and from an outer end surface of the flange part in order to have bottoms. The coil device is easy to connect a wire and has excellent bonding strength even when the connecting part becomes the mounting surface.