PURPOSE: To sharply reduce a soldering defect caused when a soldering operation is performed in an automatic soldering apparatus by a method wherein the air is blown, to a pattern face on a board conveyed by means of a conveyor, from an air nozzle arranged in a conveyance route before the automatic soldering apparatus and foreign matters are removed.

CONSTITUTION: When a board 2 which is moved on a conveyance conveyor 4A along a conveyance route 5 reaches a subconveyor 4B from the conveyance conveyor 4A, the high-pressure air of an air-pressure source 11 whose pressure has been made definite by means of a pressure adjusting valve 10 is spouted from air blowoff holes 6A in an air nozzle 6. Thereby, scraps of a board material and fibers of a sheet of paper and a cloth which have adhered to a pattern face on a board 2 and to edges of insertion holes of a chip component 12 and a resistance component 13 are removed by the air. Consequently, since foreign matters are removed by the air, it is possible to prevent soldering defects that pinholes are caused due to the foreign matters or a lead is separated from a land.