A stator of a dynamo-electric machine includes a cylindrical stator iron core having a plurality of slots arranged in a circumferential direction, and a stator winding composed of a plurality of conductor wires installed in the slots, the stator winding being formed by joining end portions of the plurality of conductor wires extending out of different ones of the slots at the end surface of the stator iron core, wherein the conductor wires are formed such that a conductor sectional area of an end portion over a predetermined extent in a lengthwise direction from a distal end thereof is smaller than a conductor sectional area of a main portion, and an insulating film covers the main portion and a part of the end portion in the vicinity of the main portion, and a plurality of the conductor wires extending out of the different slots are joined with their end portions arranged properly.