Abstract: A stator of a dynamo-electric machine which is capable of raising the space factor in each slot and which can easily be assembled incorporates first coil pieces, each of which has a width at the lower portion of the slot being smaller than the width at the upper portion of two slots; and second coil pieces arranged to be fitted to teeth adjacent to the tooth to which the first coil piece is fitted so as to be inserted into the empty space for filling the space. The first and second coil pieces are alternately inserted into the slots of the stator core. The empty space in the slot formed after the first coil piece has been inserted has sides extending parallel with the adjacent tooth or is gradually widened toward the upper portion of the slot. Therefore, the second coil piece can easily be inserted into the slot without interference with another member. Thus, the slots can be filled with the second coil pieces so that the space factor can be raised.