A surface treatment system includes a surface treatment tank, a first guide rail and a second guide rail that extend at a position offset from a position over the upper opening of the surface treatment tank, and a plurality of transfer jigs that respectively hold a workpiece and are supported by the first guide rail and the second guide rail. The transfer jig includes a horizontal arm section, a first guide target section that is guided by the first guide rail, a second guide target section that is guided by the second guide rail, and a vertical arm section that is suspended from the horizontal arm section at a position between the first guide target section and the second guide target section, and holds the workpiece.