A microbearing tester driven by an air turbine of diameter has been developed, and successfully used to test hydroinertia gas bearings with a shaft of diameter. The effects of bearing gas pressure conditions and bearing length to diameter ratio on the maximum achievable rotation speed were investigated. The maximum rotation speed of , which corresponds to the number (the product of a shaft diameter in millimeter and a rotation speed in rpm) of 3,560,000, was achieved. At , the tip speed of the turbine reaches approximately . Using the bearing system developed, the turbo components of a class gas turbine and an air pump for class fuel cells can be tested.