The tribocharge rotational speed sensor for ball bearings was developed. The tribocharge sensor having a rotor and a stator with each segmented electrodes, which sandwich a PTFE film, was attached a ball bearing. The ball bearing used in this study is the bearing number of 6201DDU. The thickness of this sensor is less than 0.5 mm. When the bearing rotates, the PTFE film on a segmented electrode of rotor rotationally slides in contact with other electrode on stator. Each segmented electrode has four segments, positively charged by sliding with the PTFE, and the PTFE film is negatively charged. Output sensor voltage is obtained from the segmented electrode of the stator attached on a fixed ring of ball bearing. The rotor is attached on a rotating ring of ball bearing. This bearing with the tribocharge sensor was evaluated using our trust type bearing tester. The output voltage from this tribocharge sensor was proportional to the rotational speed and that was about 1.5 V0p at 2000 rpm. In addition, the generated power was 0.2 μW at 2000 rpm.