A stator comprising: a stator core in which slots are formed a predetermined distance apart in a circumferential direction; and a polyphase stator coil formed by a first flat wire of a first phase and a second flat wire of a second phase that differs from the first phase, the first and second flat wires having each a rectangular cross-section, the first flat wire and the second flat wire being coated with an insulating layer, and the polyphase stator coil being wound around the stator core through the slots, wherein the first flat wire and the second flat wire each have an insertion portion that is inserted into the slots, the first flat wire and the second flat wire each have a coil end portion that protrudes from an end portion of the stator core; and a first insulating layer of an adjacent portion of the first flat wire is thicker than a second insulating layer of the first flat wire, the adjacent portion is positioned on a first flat surface of the first flat wire adjacent to the second flat wire at the coil end portion of the first flat wire, and the second insulating layer is in a region other than the coil end portion of the first flat wire; characterized in that the first insulating layer is formed by applying or dripping insulation material only on to the adjacent portion, such that the first insulating layer of the adjacent portion positioned on the first flat surface of the first flat wire is thicker than the second insulating layer being additionally on a non-adjacent portion of the first flat wire, the non-adjacent portion being positioned on the other three surfaces that are in the same region of the coil end portion as the adjacent portion in the longitudinal direction of the first flat wire. a stator core in which slots are formed a predetermined distance apart in a circumferential direction; and a polyphase stator coil formed by a first flat wire of a first phase and a second flat wire of a second phase that differs from the first phase, the first and second flat wires having each a rectangular cross-section, the first flat wire and the second flat wire being coated with an insulating layer, and the polyphase stator coil being wound around the stator core through the slots, wherein the first flat wire and the second flat wire each have an insertion portion that is inserted into the slots, the first flat wire and the second flat wire each have a coil end portion that protrudes from an end portion of the stator core; and a first insulating layer of an adjacent portion of the first flat wire is thicker than a second insulating layer of the first flat wire, the adjacent portion is positioned on a first flat surface of the first flat wire adjacent to the second flat wire at the coil end portion of the first flat wire, and the second insulating layer is in a region other than the coil end portion of the first flat wire; characterized in that the first insulating layer is formed by applying or dripping insulation material only on to the adjacent portion, such that the first insulating layer of the adjacent portion positioned on the first flat surface of the first flat wire is thicker than the second insulating layer being additionally on a non-adjacent portion of the first flat wire, the non-adjacent portion being positioned on the other three surfaces that are in the same region of the coil end portion as the adjacent portion in the longitudinal direction of the first flat wire.