A stator is applied in an electrical motor. The stator includes a hollow iron core and a plurality of coil windings. The hollow iron core has two opposite surfaces and a plurality of accommodating spaces communicated with the surfaces. The accommodating spaces are arranged in an annular pattern. Each of the coil windings includes a plurality of wires winded via the accommodating spaces. Portions of the wires of the coil windings located in the accommodating spaces are radially concentrically arranged to form a plurality of winding layers. In at least one of the accommodating spaces, a wire cross-sectional area of the wire of the innermost one of the winding layers is smaller than a wire cross-sectional area of the wire of the outermost one of the winding layers.