Provided is a multi-electrode gas-shielded single-sided arc welding method which is capable of resulting in a preferable back bead shape and effectively preventing the occurrence of high-temperature cracking. This multi-electrode gas-shielded single-sided arc welding method involves filling a groove filler into a groove formed by a pair of plates butted together, and welding by using a plurality of electrodes arranged in a row in the weld line direction. The plurality of electrodes includes a preceding electrode and a succeeding electrode that is continuous with the preceding electrode. The polarity of the preceding electrode is DCEP, and the wire type of the preceding electrode is flux-cored wire or solid wire. The polarity of the succeeding electrode is DCEN, the wire type of the succeeding electrode is flux-cored wire, and the welding current of the succeeding electrode is 180A or greater. The inter-pole distance between the preceding electrode and the succeeding electrode is 65 mm to 100 mm, inclusive. The root gap of the groove is 3 mm to 8 mm, inclusive. The surface area of a portion occupied by the groove filler on a surface orthogonal to the weld line direction is 20 mm2 to 50 mm2, inclusive.
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