To smoothly flow fluid on the central side of a rotary body by constituting an air blower device of the rotary body where plural blade bodies are protrusively formed toward the inside diameter side from an annular rim body, a casing to rotatably support the rim body and a driving device to impart motive power to the rim body to rotate the rotary body.

Cooling air to a cooling unit 1 is sent into by a cooling fan 3, but the cooling fan 3 is formed in an axial flow type constituted by using a rotary body 4 where plural blade bodies 4b are protrusively formed toward the inside diameter side from an annular rim body 4a, a casing 5 to rotatably support the rim body 4a and a driving device 6 to impart motive power to the rim body 4a to rotate the rotary body 4. A central part of the rotary body 4 is formed as an opening 4d, and the driving device 6 is arranged in an outer peripheral part of the rotary body 4. As a result, since there is nothing to hinder flow of cooling air in the central part of the rotary body 4 in the cooling fan 3, a central side flow becomes smooth, and a speed is uniformized over the whole rotary body 4.