An experimental investigation of a counter-rotating fan was conducted with special attention to the effects of the supporter shape of the electric motor and the distance between two rotors on the fluid dynamic and fan noise characteristics. A comparison of the fan noise and the fluid dynamic characteristics between the counter-rotating fan and a two-stage rotor fan was also made. As a result it was concluded that the noise generated from a symmetrically supported fan was lower by 3 to 6 dB than that from an asymmetrically supported fan, and the fluid dynamic characteristics of the former were superior to those of the latter. The larger the distance between two rotors is, the lower the fan efficiency and the fan noise are. Although the fluid dynamic characteristics of the counter-rotating fan are superior to those of the two-stage rotor fan, the counter-rotating fan can't be recommended yet because it generates from much more noise than the latter.