A jet nozzle which allows a width of a flow of jetted molten solder to be varied, comprising: a nozzle main body having a frame shape with upper and lower opening ends, the lower opening end being opposed to a soldering bath and the upper opening end jetting the molten solder flow, a part of the nozzle main body having a channel section; and a molten solder flow width varying member that varies a width of the upper opening end of the nozzle main body by a slide of the molten solder flow width varying member within the channel section of the nozzle main body to vary a width of the flow of the molten solder jetted from the upper opening end of the nozzle main body, wherein the molten solder flow width varying member includes: a molten solder flow width varying plate that extends along a jetting direction of the molten solder, and varies the width of the flow of the molten solder; a rectangular rectifying piece that is attached to the molten solder flow width varying plate at an opposite side of the upper opening end of the nozzle main body and extends along a slide direction of the molten solder flow width varying member; and a sliding shaft that slides the rectifying piece, characterized in that the rectifying piece contains a cut-away portion that is obliquely cut away from a side surface of the rectifying piece at a side of the molten solder flow width varying plate to a bottom of the rectifying piece, the cut-away portion being configured to guide the flow of the molten solder. a nozzle main body having a frame shape with upper and lower opening ends, the lower opening end being opposed to a soldering bath and the upper opening end jetting the molten solder flow, a part of the nozzle main body having a channel section; and a molten solder flow width varying member that varies a width of the upper opening end of the nozzle main body by a slide of the molten solder flow width varying member within the channel section of the nozzle main body to vary a width of the flow of the molten solder jetted from the upper opening end of the nozzle main body, wherein the molten solder flow width varying member includes: a molten solder flow width varying plate that extends along a jetting direction of the molten solder, and varies the width of the flow of the molten solder; a rectangular rectifying piece that is attached to the molten solder flow width varying plate at an opposite side of the upper opening end of the nozzle main body and extends along a slide direction of the molten solder flow width varying member; and a sliding shaft that slides the rectifying piece, a molten solder flow width varying plate that extends along a jetting direction of the molten solder, and varies the width of the flow of the molten solder; a rectangular rectifying piece that is attached to the molten solder flow width varying plate at an opposite side of the upper opening end of the nozzle main body and extends along a slide direction of the molten solder flow width varying member; and a sliding shaft that slides the rectifying piece, characterized in that the rectifying piece contains a cut-away portion that is obliquely cut away from a side surface of the rectifying piece at a side of the molten solder flow width varying plate to a bottom of the rectifying piece, the cut-away portion being configured to guide the flow of the molten solder.