To provide an inexpensive sensor excellent in the productivity with a simple constitution, which can perform the detection without any problem even when the length of the sensor is long, when a liquid flows, or when a vibration exists in a liquid container, and which can quickly cope with the change in the specifications.

In the liquid level sensor (S) in which, at one end of a coaxial cable (1) made by disposing an inner conductor and an outer conductor through the inner conductor and by coating the outer periphery of the outer conductor with an insulator layer, a pair of electrodes are formed by coating with a conductive resin the end of the inner conductor exposed at an interval in the longitudinal direction of the cable and the end of the outer conductor, and in which a flange with a mounting position fixing sleeve is provided, a member (3) for reinforcing and/or adjusting the flange mounting position is inserted on the outer insulator layer between the flange (2) and the electrode parts (1a and 1b).