Coil device and method of manufacturing coil device

A coil device comprising:

• a substrate having a first main surface and a second main surface opposed to the first main surface;
• a first insulating film provided in contact with a first direction side of the substrate, with the first direction being a direction from the second main surface to the first main surface;
• a first coil part provided in contact with a first direction side of the first insulating film and being a spiral-shaped conductive film in a plan view seen from a direction opposite to the first direction;
• a second insulating film provided to cover a first direction side of the first coil part and the first direction side of the first insulating film where the first coil part is not provided;
• a second coil part being a spiral-shaped conductive film in the plan view and provided in contact with a first direction side of the second insulating film;
• at least one first groove provided on the second insulating film in a region inside an outer peripheral edge of the second coil part in the plan view and having a width in the first direction on a surface on the first direction side of the second insulating film;
• and
• at least one second groove provided on the surface on the first direction side of the second insulating film and having a width in the first direction in a region outside the outer peripheral edge of the second coil part in the plan view.