An air conditioner comprising a housing and a centrifugal blower accommodated in the housing, the housing having an air outlet formed in a portion of a first side surface of the housing and an air inlet formed in a portion of a second side surface of the housing opposite to the first side surface, the centrifugal blower comprising: a casing; and a centrifugal fan housed in the casing, the casing having an outlet formed in a radial direction perpendicular to a rotational axis of the centrifugal fan, the casing having a first wall facing the centrifugal fan, the first wall having an opening for taking in air, the opening being formed in a portion of the first wall, the portion being crossed by the rotational axis of the centrifugal fan, the first wall having a bell mouth surrounding the opening, the bell mouth having a first region and a second region, the first region being disposed closest to the air inlet and the second region being disposed farther from the air inlet than the first region is from the air inlet, the second region being a portion adjacent to a tongue located forward of the outlet in a direction of rotation of the centrifugal fan in the direction of rotation, the bell mouth comprising in each of the first region and the second region, an end defining an outer perimeter of the opening, and a surface which is curved and extends from the end to be away from the centrifugal fan, a distance from the rotational axis of the centrifugal fan to the end in the first region being greater than a distance from the rotational axis to the end in the second region, wherein the rotational axis is disposed to extend parallel to the portion of the first side surface and the portion of the second side surface; a curvature of the surface of the first region in a cross section of the first region including the rotational axis being smaller than a curvature of the surface of the second region in a cross section of the second region including the rotational axis. a casing; and a centrifugal fan housed in the casing, the casing having an outlet formed in a radial direction perpendicular to a rotational axis of the centrifugal fan, the casing having a first wall facing the centrifugal fan, the first wall having an opening for taking in air, the opening being formed in a portion of the first wall, the portion being crossed by the rotational axis of the centrifugal fan, the first wall having a bell mouth surrounding the opening, the bell mouth having a first region and a second region, the first region being disposed closest to the air inlet and the second region being disposed farther from the air inlet than the first region is from the air inlet, the second region being a portion adjacent to a tongue located forward of the outlet in a direction of rotation of the centrifugal fan in the direction of rotation, the bell mouth comprising in each of the first region and the second region, an end defining an outer perimeter of the opening, and a surface which is curved and extends from the end to be away from the centrifugal fan, an end defining an outer perimeter of the opening, and a surface which is curved and extends from the end to be away from the centrifugal fan, a distance from the rotational axis of the centrifugal fan to the end in the first region being greater than a distance from the rotational axis to the end in the second region, wherein the rotational axis is disposed to extend parallel to the portion of the first side surface and the portion of the second side surface; a curvature of the surface of the first region in a cross section of the first region including the rotational axis being smaller than a curvature of the surface of the second region in a cross section of the second region including the rotational axis.