An oval nugget can reliably be obtained with this indirect spot welding method. In this indirect spot welding method, an electrode end portion of a welding electrode includes a tip of the welding electrode, and as viewed from the tip, the electrode end portion has a two-step dome shape formed by a first curved surface with a curvature radius r1 (mm) located within a range of a circle of radius R (mm) centering on the tip and a second curved surface with a curvature radius r2 (mm). 2√t≤R≤6√t (1), 30≤r1 (2), and 6≤r2≤12 (3), where t is the sheet thickness (mm) of a thinner metal sheet.