An armature winding is configured by mounting into an armature core a plurality of distributed-winding coils that are each produced by bending and shaping a conductor wire that is coated with insulation, coil ends are configured by arranging coil end portion rows that are formed by arranging coil end portions of the coils in a single row circumferentially in n layers in a radial direction, where n is an integer that is greater than or equal to 1, and an interphase insulating material includes: a strip-shaped insulating sheet material that is inserted inside the coil end portions, and that is disposed so as to extend circumferentially between the coil end portion rows; and an insulating buffering material that is formed on one surface of the insulating sheet material, and that is fixed to the coil end portion rows by forming air bubble groups internally.