To provide a MIG welded joint for aluminum and steel having enhanced soundness of a weld zone and excellent joint strength, and to provide a MIG welding process for aluminum material and steel by which soundness of a weld zone can be effectively enhanced by controlling heat input so as to be reduced when the MIG welding is performed by overlapping the aluminum material and steel different in material one on another.

The MIG welded joint for the aluminum material and the steel is obtained by overlapping the aluminum material 12 and the steel 14 one on another and subjecting an end face part of the aluminum material 12 to the predetermined DC pulse MIG welding operation using a welding wire 24 made of 4000 or 5000 series aluminum alloy, wherein the aluminum material has a thickness P of 0.5-2.0 mm, the steel 14 has a thickness Q satisfying 0.6Q/P0.8, the welding wire 24 has a diameter L of 0.8-1.6 mm, and the penetration depth of the steel is 5% of the thickness of the steel.