The present embodiment comprises: a rotary shaft; a rotor mounted on the rotary shaft; a stator for encompassing the outer circumference of the rotor; an impeller mounted on the rotary shaft so as to be spaced from the rotor; a bearing housing having a through-hole through which the rotary shaft passes; a rolling bearing disposed in the bearing housing and coupled to the rotary shaft; and a gas bearing disposed in the bearing housing so as to be spaced from the rolling bearing in an axial direction, and facing the outer circumference of the rotary shaft.