To sent the same air as that an axial fan with a sirocco fan by arranging sectional casings which are communicated with an air suction port, and which is arranged shifting each other in a circumferential direction, and arranging air diffusers every side wall surfaces of an air suction side and side walls of a side opposite thereto.

In an electric dust collector, a pre-filter, an ionizer a collector and an after filter are arranged from an air intake port side in order, and a sirocco fan 31 which is covered with a fan casing 21 and which is connected to a driving shaft 23 of a fan motor 22 is arranged downstream therefrom. The fan casing 21 is separated into two steps in an intake direction 25 of air, and is constituted by separating casings 28A, 28B communicated with an air intake port 26. Respective separation casings 28A, 28B are arranged shifting to an upper and lower parts of a circumferential direction around a shaft 27 of intake air. Air diffusion ports 30A, 30B are arranged on side wall surfaces 29A, 29 of a side wall surface of the air intake side and a side opposite thereto.