Axial-flow fan

An axial-flow fan comprising:

• a central hub connected with a driving shaft of a motor;
• and
• a plurality of blades extending radially along the circumference of the hub for blowing air toward an axial direction, the plurality of blades integrated with the hub into a single body,
• wherein each blade has a backward sweep angle at the blade root thereof and a forward sweep angle at the blade tip thereof, while having an airflow distributing region that is defined by a plurality of small regions where sweep angles are changed in turn formed on a region between the backward sweep angle region and the forward sweep angle region, and
• wherein assuming that a camber ratio at the blade root(cr1) of each blade is the value obtained by dividing a maximum camber value at the blade root into a chord length, a camber ratio at the blade tip(cr2) of each blade is the value obtained by dividing a maximum camber value at the blade tip into the chord length, and a percentage of decrease of the camber ratio is the value obtained by dividing a difference value between the camber ratio at the blade root(cr1) and the camber ratio at the blade tip(cr2) into the camber ratio at the blade root(cr1), the percentage of decrease of the camber ratio is in a range between 33% and 85%.