1. A cooling jacket on a radial outside of a stator of a rotary electric machine, the cooling jacket comprising:
a tubular main body including a first end face of one axial side and a second end face of the other axial side; and
a groove unit defining a flow channel of a cooling medium, the groove unit being successively disposed axially on an outer
periphery of the main body,
wherein the cooling jacket includes no portion located radially outward from a bottom of the groove unit between a first end
portion of the groove unit on the one axial side of the main body and the first end face of the main body and between a second
end portion of the groove unit on the other axial side of the main body and the second end face of the main body,
wherein the groove unit is a multi-thread groove successively extended axially on the main body in a spiral manner.