A stator (100) of an electric motor includes a coil (12), a stator core (10) which supports the coil, and covers (22a, 22b) which are attached to the stator core so as to surround coil ends (13a, 13b) of the coil, wherein the covers have outside diameters which are at least partially smaller than the outside diameters of the stator cores, the covers have coefficients of linear expansion which are larger than the coefficient of linear expansion of the stator core, and the covers expand due to heat whereby the covers closely contact the housing which is arranged around the stator.