An iron core is configured as a winding iron core block group that is obtained in such a manner that winding iron core blocks having rectangular cross-sections each of which is obtained by laminating magnetic metal ribbons with a predetermined width and which have plural widths and laminated thicknesses are arranged in the width direction of the magnetic metal ribbons. The laminated thickness of the winding iron core block located in the middle of the width direction of the magnetic metal ribbons is larger, and the cross-section of each iron core leg is configured substantially in a circular shape by centering the winding iron core blocks in the laminated direction of the magnetic metal ribbons. Upper and lower yokes are arranged in such a manner that the bottom faces of the winding iron core blocks are aligned, and an in-window support member supports the upper yoke on a plane.