An electric rotating machine as disclosed herein includes an armature core having an outer peripheral portion with slots, a rotatable shaft having an outer periphery and rotatably supporting the armature core, a plurality of lower layer coils each having at opposite ends thereof respective lower layer coil protrusion portions, and a plurality of upper layer coils disposed radially outside of the lower layer coils and each having at opposite ends thereof respective upper layer coil protrusion portions. According to the novel method of this invention, the lower layer coil protrusion portions are bonded to the upper layer coil protrusion portions with a welding torch of an arc welding machine by radially moving at least one of the welding torch and boundary portions, at which the corresponding protrusion portions abut one another, relative to each other. By radially moving the welding torch and the boundary portions relative to each other, circumferentially adjacent bonded protrusion portions are smaller, mechanically stronger, and do not abut against one another.