High pressure and large flow rate small-sized cooling fans are used for servers in data centers and there is a strong demand to increase its performance because of increase of quantity of heat from servers. Therefore, high rotational speed design is conducted, and rotational speed over 10,000min-1 is employed for cooling fans of servers. Contra-rotating rotors have been adopted for some of high pressure and large flow rate cooling fans to meet the demand. The company's research and development period for the contra-rotating small-sized cooling fan is short and its internal flow condition is not clarified well. Therefore, the internal flow condition was investigated by the numerical analysis. In the present paper, fan static pressure curves of the contra-rotating small-sized cooling fan with a 40mm square casing are shown by the experimental. Furthermore, the influences of the geometrical shape and design specification of the contra-rotating small-sized cooling fan on the internal flow condition are clarified by the numerical analysis.