Small-sized axial fan is used as air cooler for electric equipments. But there is demand for higher power of fan according to the increase of quantity of heat from electric device. Therefore, higher rotational speed design is necessary but it causes the deterioration of efficiency and increases the noise. Then the adoption of contra-rotating rotor for small-sized fan was proposed for the improvement of performance. In the present paper, experiment and numerical flow simulation was conducted to investigate the performance of conventional small-sized axial fan and contra-rotating small-sized axial fan. And internal flow field and pressure distribution were clarified from the numerical results then the effect of contra-rotating type on the performance and the similarity law of small-sized axial fan would be discussed.