1. An arc welding quality evaluation apparatus characterized in that, in consumable electrode gas-shielded arc welding, wherein a welding voltage is applied between a welding wire and a workpiece to be welded, molten metal droplets from the welding wire are transferred to the workpiece, and that portion of the wire consumed by the transfer of droplets is replenished, for performing continuous arc welding, it comprises a heat input detection means for detecting heat input applied to the workpiece, from the welding voltage applied thereto and welding current supplied thereto; a welding time detection means for detecting workpiece welding time; a spatter weight detection means for detecting the weight of spatter produced during the workpiece welding time; a heat compensation means for compensating for heat loss due to spattering during the workpiece welding time; an effective heat input computation means for computing effective heat input based on detected values of the heat input detection means and welding time detection means, and a heat compensation value of the heat compensation means; and a weld quality assessment means for assessing weld quality acceptability based on the degree of separation of an output of the effective heat input computation means from a reference standard value.