A soldering device, comprising: a first treatment part in which a component, having an electrode to be soldered, is set; a second treatment part that is separated in a sealable manner by a first opening-closing unit, which is provided between the first treatment part and the second treatment part, and that is configured to send out the component, which is fed from the first treatment part, to the subsequent third treatment part; a third treatment part that is separated in a sealable manner by a second opening-closing unit, which is provided between the second treatment part and the third treatment part, and that is configured to cause the component, which is fed from the second treatment part, to make contact with an organic fatty acid-containing solution, and that is configured to move the component horizontally; a fourth treatment part that has a molten solder adhesion unit that is configured to move the component, which has been moved horizontally by the third treatment part, to an upper space portion and that is configured to cause the molten solder to be adhered onto the electrode and a molten solder removal unit that is configured to remove excessive molten solder out of the molten solder adhered in the space portion; a fifth treatment part that is configured to move the component horizontally, which has been moved downward in the fourth treatment part; a sixth treatment part that is separated in a sealable manner by a third opening-closing unit, which is provided between the fifth treatment part and the sixth treatment part, and that is configured to send out the component, which is fed from the fifth treatment part, to the subsequent seventh treatment part; a seventh treatment part that is separated in a sealable manner by a fourth opening-closing unit, which is provided between the sixth treatment part and the seventh treatment part, and that is configured to take out the component, which is fed from the sixth treatment part, a first cassette conveying device that is configured to move a cassette, loaded with the component, between the second treatment part and the third treatment part; and a second cassette conveying device that is configured to move a cassette, loaded with the component, between the fifth treatment part and the sixth treatment part, wherein the first opening-closing unit and the second opening-closing unit are controlled such that the first opening-closing unit and the second opening-closing unit do not open at the same time, and the third opening-closing unit and the fourth opening-closing unit are controlled such that the third opening-closing unit and the fourth opening-closing unit do not open at the same time. a first treatment part in which a component, having an electrode to be soldered, is set; a second treatment part that is separated in a sealable manner by a first opening-closing unit, which is provided between the first treatment part and the second treatment part, and that is configured to send out the component, which is fed from the first treatment part, to the subsequent third treatment part; a third treatment part that is separated in a sealable manner by a second opening-closing unit, which is provided between the second treatment part and the third treatment part, and that is configured to cause the component, which is fed from the second treatment part, to make contact with an organic fatty acid-containing solution, and that is configured to move the component horizontally; a fourth treatment part that has a molten solder adhesion unit that is configured to move the component, which has been moved horizontally by the third treatment part, to an upper space portion and that is configured to cause the molten solder to be adhered onto the electrode and a molten solder removal unit that is configured to remove excessive molten solder out of the molten solder adhered in the space portion; a fifth treatment part that is configured to move the component horizontally, which has been moved downward in the fourth treatment part; a sixth treatment part that is separated in a sealable manner by a third opening-closing unit, which is provided between the fifth treatment part and the sixth treatment part, and that is configured to send out the component, which is fed from the fifth treatment part, to the subsequent seventh treatment part; a seventh treatment part that is separated in a sealable manner by a fourth opening-closing unit, which is provided between the sixth treatment part and the seventh treatment part, and that is configured to take out the component, which is fed from the sixth treatment part, a first cassette conveying device that is configured to move a cassette, loaded with the component, between the second treatment part and the third treatment part; and a second cassette conveying device that is configured to move a cassette, loaded with the component, between the fifth treatment part and the sixth treatment part