In this study, we proposed a novel concept of liquid level indicator that can stably measure the liquid level even with changes in liquid density by enormous temperature changes. This uses a distributed optical fiber sensor based on Rayleigh scattering with high spatial resolution. Additionally, taking advantage of the flexibility of an optical fiber sensor, we introduced a bendable supporting structure and made it possible to freely adjust the angle for ease of installation of the liquid level indicator. In the proof-of-concept experiment using a prototype incorporating the proposed concept, we confirmed that the interface location can be effectively detected by utilizing the difference in heat transfer characteristics between liquid and gas phases, demonstrating the feasibility of liquid level measurement. Such a liquid level indicator is expected to enable more accurate level measurements in environments with huge temperature changes and to be conveniently used even in situations where installation and maintenance of the level meter are challenging due to complex internal structures.