An outdoor unit, comprising: a cabinet; a bell mouth provided in the cabinet; a fan guard provided at an outlet of the bell mouth; and a fan motor assembly fixed to the fan guard, wherein the fan guard includes: a hub located at a centre of the outlet and having the fan motor assembly fixed thereto; and a rib connecting the hub and the cabinet, wherein a height of the rib in a direction parallel to a rotation axis of the fan motor assembly increases outwardly from the hub, wherein the hub has an insertion groove having a predetermined depth on a rear surface of the hub, and the fan motor assembly is inserted into the insertion groove, wherein the fan motor assembly includes: a motor fixed to the hub; and a blower fan driven by the motor; and wherein the rib includes: a first end surface corresponding to a position where it is connected to the hub, a second end surface corresponding to a position at which the rib is adjacent to a tip of a blade of the blower fan, and a third end surface located between the first end surface and the second end surface, at the same distance from the first end surface and the second end surface, respectively, wherein the first end surface has a height of 0.02 to 0.09 times a distance L from a centre of the hub to the tip of the blade, the second end surface has a height of 0.04 to 0.2 times the distance L, and the third end surface has a height of 0.03 to 0.14 times the distance L from the centre of the hub to the tip of the blade, and wherein the rib is provided so that a tilt angle of a cross-section thereof increases with distance from the hub with respect to a driving shaft of the motor, wherein the first end surface has a tilt angle of 10° to 30° and the second end surface has a tilt angle of 20° to 40°, and the third end surface has a tilt angle of 15° to 35°. a cabinet; a bell mouth provided in the cabinet; a fan guard provided at an outlet of the bell mouth; and a fan motor assembly fixed to the fan guard, wherein the fan guard includes: a hub located at a centre of the outlet and having the fan motor assembly fixed thereto; and a rib connecting the hub and the cabinet, a hub located at a centre of the outlet and having the fan motor assembly fixed thereto; and a rib connecting the hub and the cabinet, wherein a height of the rib in a direction parallel to a rotation axis of the fan motor assembly increases outwardly from the hub, wherein the hub has an insertion groove having a predetermined depth on a rear surface of the hub, and the fan motor assembly is inserted into the insertion groove, wherein the fan motor assembly includes: a motor fixed to the hub; and a blower fan driven by the motor; and a motor fixed to the hub; and a blower fan driven by the motor; and wherein the rib includes: a first end surface corresponding to a position where it is connected to the hub, a second end surface corresponding to a position at which the rib is adjacent to a tip of a blade of the blower fan, and a third end surface located between the first end surface and a first end surface corresponding to a position where it is connected to the hub, a second end surface corresponding to a position at which the rib is adjacent to a tip of a blade of the blower fan, and a third end surface located between the first end surface and the second end surface, at the same distance from the first end surface and the second end surface, respectively, wherein the first end surface has a height of 0.02 to 0.09 times a distance L from a centre of the hub to the tip of the blade, the second end surface has a height of 0.04 to 0.2 times the distance L, and the third end surface has a height of 0.03 to 0.14 times the distance L from the centre of the hub to the tip of the blade, and wherein the rib is provided so that a tilt angle of a cross-section thereof increases with distance from the hub with respect to a driving shaft of the motor, wherein the first end surface has a tilt angle of 10° to 30° and the second end surface has a tilt angle of 20° to 40°, and the third end surface has a tilt angle of 15° to 35°.