The bending and surface durability tests were first carried out using case-carburized pre-alloy sintered steel gears with different densities from 7.2g/cm3 to 7.55g/cm3. The load bearing capacities of as-sintered gears with a density above7.4 g/cm3 were almost matched those of case-carburized Cr-Mo wrought steel gear, and the gear surface rolling increased the strength limits by 5~20%. Then, these experimental results were analytically investigated by examining the maximum normal and shear stresses in the surface layer near the critical stress section using FE-simulation model considering voids. The stress distributions tend to increase as the density of P/M material became smaller and gradually decrease as the amount of fully densified depth increased. Thus, there was only a slight difference in peak stress values among the surface rolled gears with a density above 7.4g/cm3. These simulation results seemed to explain the experimental results well.