Abstract: An induction coil composed of n pieces of identically shaped coil elements (where n is equal to or greater than two), which are rotation-symmetrically arranged with respect to an axis normal to the surface of an object to be processed, is provided above the object, the coil elements being electrically connected in parallel. Each of the coil elements of the induction coil encircles the aforementioned axis, with the ground end and the feed end located at the same position on a projection plane on the object with the ground end under the feed end. Each coil element has a bottom portion shaped like an arc having a predetermined width and a central angle of 360°/n, with the ground end at one end thereof, and a feed portion shaped like an arc having a predetermined width, with the feed end at one end thereof, the feed portion being located above the bottom portion and electrically connected to the same bottom portion.

Abstract: An induction coil composed of n pieces of identically shaped coil elements (where n is equal to or greater than two), which are rotation-symmetrically arranged with respect to an axis normal to the surface of an object to be processed, is provided above the object, the coil elements being electrically connected in parallel. Each of the coil elements of the induction coil encircles the aforementioned axis, with the ground end and the feed end located at the same position on a projection plane on the object with the ground end under the feed end. Each coil element has a bottom portion shaped like an arc having a predetermined width and a central angle of 360°/n, with the ground end at one end thereof, and a feed portion shaped like an arc having a predetermined width, with the feed end at one end thereof, the feed portion being located above the bottom portion and electrically connected to the same bottom portion.