Oil fences are marine pollution response materials designed for rapid deployment to contain oil spills. In this study, we developed a self-inflating folding oil fence that can be easily loaded and operated on a small patrol or small oil spill response vessel. It is automatically inflated by a built-in spring without any additional air injection, and maintains a stable triangular upright position due to the buoyant body attached to the top of the internal structure. We confirmed that it meets the type approval standards for domestic oil fence Type A (freeboard 20-30 cm, draft 30-40 cm). Functionality was verified through wave basin and sea trials. Durability tests of the tension spring, a key component, demonstrated that it withstood a 10,000-cycle fatigue test and saltwater immersion without any performance degradation. The development of this equipment will enhance response capabilities for marine oil spills and contribute to the marine oil spill response industry worldwide.