The applicability of flexible OLED devices has been expanding to rollable or foldable displays and lighting. At this time, a system to measure the durability of flexible OLEDs needs to be developed to successfully launch flexible OLEDs in future electronic devices. In this paper, we develop a bending lifetime tester to measure the performance of flexible OLEDs by measuring the luminance of the device in real-time during the bending test. A fixed distance between the bent OLEDs and detector during the bending test improves the accuracy of the measured brightness in real time. This bending tester can measure the lifetime of flexible OLEDs with a mean deviation of less than 0.23% over a temperature range of -30 to 80℃. This performance is sufficient to measure the accelerated lifetime test of flexible OLEDs for reliability engineering.