Multi-blade fan for air-cooled engine

In a multi-blade fan for an air-cooled engine, by defining the inlet angle β and the angle β′ to make the sum thereof less than 80° (preferably defining β as 32° and β′ as 36°), the multi-blade fan achieves greater air volume than in the case where the sum is made 80° or greater, where β is the angle between the relative velocity direction and the peripheral direction on the inlet side of the blades, β is the angle between the relative velocity direction and the peripheral direction on the outlet side of the blades, and β′ is the difference obtained by subtracting β from 180°. The number of blades can therefore be reduced to realize lower noise level while still maintaining the same air volume as the prior art multi-blade fan.