A motor assembly comprising: a motor housing having an inner circumferential face; a rotation shaft having a first support portion and a second support portion; an impeller mounted on a portion of the rotation shaft; a rotor mounted on the rotation shaft and spaced apart from the impeller axially along a rotational axis of the rotation shaft; a stator surrounding the rotor and spaced apart from the rotor radially relative to the rotational axis of the rotation shaft, wherein the stator is mounted on the inner circumferential face of the motor housing; a rolling bearing mounted on the rotation shaft between the impeller and the rotor and rotatably supporting the first support portion of the rotation shaft; a gas bearing bracket disposed in the motor housing and receiving the second support portion of the rotation shaft; and a gas bearing assembly received in the gas bearing bracket and rotatably supporting the second support portion of the rotation shaft, wherein the gas bearing assembly includes a gas bearing surrounding the second support portion of the rotation shaft and configured to be spaced apart from the second support portion of the rotation shaft to define a gap between the gas bearing and the second support portion during rotation of the rotation shaft, characterized in that the gas bearing assembly further includes: a bush that surrounds an outer circumferential face of the gas bearing, wherein the gas bearing is press-fitted into an inner circumferential face of the bush, a fixing groove defined in an outer circumferential face of the bush, and an elastic member seated in the fixing groove and interposed between the inner circumferential face of the gas bearing bracket and the outer circumferential face of the gas bearing to elastically support the gas bearing, wherein the gas bearing bracket includes a first step overlapping with at least a portion of the bush with respect to an axial direction of the rotation shaft so that the gas bearing assembly is prevented from being detached in the direction from an interior of the gas bearing bracket toward the impeller. a motor housing having an inner circumferential face; a rotation shaft having a first support portion and a second support portion; an impeller mounted on a portion of the rotation shaft; a rotor mounted on the rotation shaft and spaced apart from the impeller axially along a rotational axis of the rotation shaft; a stator surrounding the rotor and spaced apart from the rotor radially relative to the rotational axis of the rotation shaft, wherein the stator is mounted on the inner circumferential face of the motor housing; a rolling bearing mounted on the rotation shaft between the impeller and the rotor and rotatably supporting the first support portion of the rotation shaft; a gas bearing bracket disposed in the motor housing and receiving the second support portion of the rotation shaft; and a gas bearing assembly received in the gas bearing bracket and rotatably supporting the second support portion of the rotation shaft, wherein the gas bearing assembly includes a gas bearing surrounding the second support portion of the rotation shaft and configured to be spaced apart from the second support portion of the rotation shaft to define a gap between the gas bearing and the second support portion during rotation of the rotation shaft, characterized in that the gas bearing assembly further includes: a bush that surrounds an outer circumferential face of the gas bearing, wherein the gas bearing is press-fitted into an inner circumferential face of the bush, a fixing groove defined in an outer circumferential face of the bush, and an elastic member seated in the fixing groove and interposed between the inner circumferential face of the gas bearing bracket and the outer circumferential face of the gas bearing to elastically support the gas bearing, wherein the gas bearing bracket includes a first step overlapping with at least a portion of the bush with respect to an axial direction of the rotation shaft so that the gas bearing assembly is prevented from being detached in the direction from an interior of the gas bearing bracket toward the impeller. a bush that surrounds an outer circumferential face of the gas bearing, wherein the gas bearing is press-fitted into an inner circumferential face of the bush, a fixing groove defined in an outer circumferential face of the bush, and an elastic member seated in the fixing groove and interposed between the inner circumferential face of the gas bearing bracket and the outer circumferential face of the gas bearing to elastically support the gas bearing, wherein the gas bearing bracket includes a first step overlapping with at least a portion of the bush with respect to an axial direction of the rotation shaft so that the gas bearing assembly is prevented from being detached in the direction from an interior of the gas bearing bracket toward the impeller.