The air-blow working machine comprises a fan (10) provided in a fan casing (30) and a drive unit (20) to drive the fan, and discharges an airflow generated by the rotating fan. The fan casing has an inner wall (31) 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 (38) 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.
