Cracking and stripping-off of solder are prevented from occurring at a solder joint. With regard to a printed board or a carrier for holding a printed board, a conveyance section conveys a printed board or a carrier in a predetermined direction, and a soldering section performs soldering on the printed board conveyed by the conveyance section. The conveyance section consists of a plurality of roller members for conveying a printed board or a carrier. The roller members roll to assist the movement of a printed board or a carrier mounted thereon. Consequently, factors, such as ruts or irregularities, for giving vibration to a printed board or a carrier are eliminated, and transmission of vibration from the conveyance section to the printed board can be prevented. As a result, solder formed on a printed board can be prevented from being cracked or stripped off.