Centrifugal Air Blower

There is provided a centrifugal air blower capable of maintaining strength of a case body and having high handleability and reliability even when an exhaust port is provided to a radial-direction side surface of the case body, and securing air volume and static pressure and reducing noise even in a small and flat shape. In an annular air blowing path formed to circle around a case body at a radial-direction outer side by a first case and a second case being assembled together, a radial-direction side surface of the second case is provided with an exhaust port partitioned by a diffuser . The diffuser is formed upright at a bottom plate forming a second air blowing path and is coupled to an annular end part arranged at a radial-direction outer side.