<p>To provide an optical fiber sensor that can detect the liquid level or detect the property of liquid with high reliability even under a frequently vibrational environment. An optical fiber sensor includes an optical fiber that includes a core having an area where a grating is formed and a clad, and is disposed so that at least a part of the area with the grating is immersed in liquid, a light source for making incident to the optical fiber a light of a wavelength band of a cladding mode at the grating, and a light receiving unit for detecting the intensity of light which is incident from the light source to the optical fiber and transmitted through the grating, and is used to detect the liquid level of the liquid or the property of the liquid.</p>
