To reduce stress applied from an air-core coil, to a conductive pattern, and effectively mount the air-core coil on a printed board, and reduce the space factor volume when the coil is fixed on the printed board.

An air-core coil 10 which is constituted by winding a wire without arranging a core on the inside has lead parts 11 where the respective end portions of the wire are linearly led out in the same direction. In a printed board 20 on which the air-core coil 10 is mounted, a pair of through holes 21 into which the respective lead parts 11 are inserted are formed. The inner peripheral surfaces of the respective through holes 21 are electrically conducted with a conducting pattern 22 arranged on the surface of the printed board 20. The tip parts of the respective lead parts 11 of the air-core coil 10 are positioned in the respective through holes 21 of the printed board 20, and the tip parts of the respective lead parts 11 and the inner peripheral surfaces of the through holes 21 are soldered.