An apparatus coats flux on a projection of a part mounted on a printed circuit board. The projection passes through the printed circuit board and projects from the printed circuit board. The apparatus contains a printed-circuit-board-holding member that holds the printed circuit board, a nozzle having an opening through which the projection comes in the nozzle and comes off the nozzle, a nozzle-moving member that moves the nozzle to a predetermined position, and a flux-supplying member that supplies the flux to the nozzle. The flux is coated on at least the projection by dipping the projection in the flux contained in the nozzle through the opening.