A blower fan is a device for forcedly producing air current. Particularly, a turbo fan that is one of the blower fans is designed to induce air in an axial direction, allow the induced air to make a turn by 90° and forcedly blow the same in a radial direction thereof. The blower fan includes a shroud formed on an air inducing side, a hub formed on an air discharge side, and a plurality of blades fixed between the shroud and the hub. To improve the productivity of the blower fan in a molding process and increase an airflow rate, the blower fan is designed having an inner diameter less than an outer diameter of the hub. In addition, the blade is designed having an outer diameter greater than that of the hub. The hub formed on the air discharge side functions to guide airflow such that air can effectively discharged, changing its flow direction by the blades. For the production convenience, an outer end of the blade is formed perpendicular to the hub and shroud. When the hub is designed having the outer diameter less than that of the blade, airflow of the air passing the blower fan cannot be sufficiently guided. That is, although the air current is forcedly formed by the blades, there may be a non-guide area where the airflow cannot be guided by the hub. Particularly, eddy current is increased in the non-guide area. This causes the noise to be increased.