Flexible MicroLEDs hold great promise as a novel tool for advancing optogenetics, enabling applications in biology. Such applications require the technology to assemble MicroLEDs onto ultra‐thin biocompatible films that conform to the delicate and uneven brain and biological tissues. In this study, a batch transfer technique using thermal release sheets is propsed. By optimizing the gate structures that support the hollow structure, a method to transfer MicroLEDs to the film without causing damage is established. It is successfully demonstrated that the flexible MicroLED films, fabricated using this technique, can be placed on the brain surface of transgenic mice and induce neural activity through optogenetic stimulation.