A soldering device according to an embodiment includes a jet nozzle and a cover. The jet nozzle jets a molten solder. The cover is filled with an inert gas in an inside thereof and has a hole part at a position that corresponds to the jet nozzle. The cover causes the jet nozzle to protrude from the hole part for an application time period when the solder is applied to an application target and houses the jet nozzle in the inside thereof for a waiting time period other than the application time period.