A coil includes: a series of turns constituted by a first turn to an n-th turn of a conductive wire having a polygonal cross-section, where n is an integer equal to or larger than 3, and the conductive wire is wound in a spiral shape and is stacked in a direction from downward toward upward; and an insulating member disposed on either an upper surface or a lower surface of an i-th turn, where i is an integer satisfying 1≤i≤n.