An air blower comprising: a rotatable impeller; a fan housing in which the impeller is disposed, the fan housing comprising first and second inlets (122h, 124h) sucking an air current along a rotation axis of the impeller and an outlet exhausting an air current in a direction perpendicular to the rotation axis; a motor disposed outside the fan housing; and a driving shaft extending along the rotation axis configured to be connected to the impeller, the driving shaft being rotated by the motor; wherein, the fan housing comprises: a first plate at which the first inlet is formed; a second plate providing a space between the first plate and the second plate to accommodate the impeller, the second plate at which the second inlet is formed; and a sidewall connecting the first plate to the second plate, the sidewall extending at an outer side of the impeller in a circumferential direction to guide air sucked through the first and second inlets (122h, 124h) to the outlet, and the impeller comprises: a main plate coupled to the driving shaft, the main plate having a first side facing the first inlet and a second side facing the second inlet; a plurality of first blades arranged on the first side in a circumferential direction; and a plurality of second blades arranged on the second side in a circumferential direction, and the motor is disposed at the first inlet side, the sidewall comprises a convex part protruding away from the rotation axis, and on arbitrary cross-sectional surfaces of the convex part in a parallel direction with the rotation axis, in each cross-sectional surface, each of points of an inner circumferential surface of the convex part, which has a maximum distance from the rotation axis, locates closer to the first plate than to the second plate, wherein a distance between the first plate and the second plate is increased toward the outlet. a rotatable impeller; a fan housing in which the impeller is disposed, the fan housing comprising first and second inlets (122h, 124h) sucking an air current along a rotation axis of the impeller and an outlet exhausting an air current in a direction perpendicular to the rotation axis; a motor disposed outside the fan housing; and a driving shaft extending along the rotation axis configured to be connected to the impeller, the driving shaft being rotated by the motor; wherein, the fan housing comprises: a first plate at which the first inlet is formed; a second plate providing a space between the first plate and the second plate to accommodate the impeller, the second plate at which the second inlet is formed; and a sidewall connecting the first plate to the second plate, the sidewall extending at an outer side of the impeller in a circumferential direction to guide air sucked through the first and second inlets (122h, 124h) to the outlet, and a first plate at which the first inlet is formed; a second plate providing a space between the first plate and the second plate to accommodate the impeller, the second plate at which the second inlet is formed; and a sidewall connecting the first plate to the second plate, the sidewall extending at an outer side of the impeller in a circumferential direction to guide air sucked through the first and second inlets (122h, 124h) to the outlet, and the impeller comprises: a main plate coupled to the driving shaft, the main plate having a first side facing the first inlet and a second side facing the second inlet; a plurality of first blades arranged on the first side in a circumferential direction; and a plurality of second blades arranged on the second side in a circumferential direction, and a main plate coupled to the driving shaft, the main plate having a first side facing the first inlet and a second side facing the second inlet; a plurality of first blades arranged on the first side in a circumferential direction; and a plurality of second blades arranged on the second side in a circumferential direction, and the motor is disposed at the first inlet side, the sidewall comprises a convex part protruding away from the rotation axis, and on arbitrary cross-sectional surfaces of the convex part in a parallel direction with the rotation axis, in each cross-sectional surface, each of points of an inner circumferential surface of the convex part, which has a maximum distance from the rotation axis, locates closer to the first plate than to the second plate, wherein a distance between the first plate and the second plate is increased toward the outlet.