The air-blow working machine comprises a fan provided in a fan casing and a drive unit to drive the fan, and discharges an airflow generated by the rotating fan. The fan casing has an inner wall disposed between the fan and the drive unit. A smooth surface is formed on the face of the inner wall on the side of the fan. A first concavo-convex portion is formed on the face of the inner wall on the side of the drive unit. Thereby, a noise is reduced without an influence upon performance for blowing air.
