Spot welding method and spot welding apparatus

A spot welding method for spot-welding a stacked assembly of at least three workpieces, comprising the steps of:

• gripping the stacked assembly between a first welding tip and a second welding tip, and electrically connecting an inner workpiece, which is positioned inside of the stacked assembly, of two of the workpieces that exhibit a maximum contact resistance in the stacked assembly, to a ground electrode, or to an electrode which is of the same polarity as the second welding tip positioned in proximity to an outer workpiece, which is positioned adjacent to the inner workpiece and faces outwardly from the stacked assembly, of the two of the workpieces;
• passing an electric current from the first welding tip toward the second welding tip thereby to generate an electric current flowing from the first welding tip through the inner workpiece toward the ground electrode or toward the electrode, and pressing the stacked assembly under a first pressing force by the first welding tip and the second welding tip thereby to join the inner workpiece to another one of the workpieces;
• and
• pressing the stacked assembly under a second pressing force which is greater than the first pressing force, thereby to join the inner workpiece to the outer workpiece.