In a liquid level detector, a first clearance may expand as at least one of a rotator and a supporter swells with a target liquid. The first clearance may be a smaller one of an inner clearance between an inner circumference side of a first guide rail and an inner circumference portion and an outer clearance between an outer circumference side of the first guide rail and the outer circumference portion, in a state where the rotator and the supporter are not swelled with the target liquid. A second clearance may contract to become smaller than the first clearance as at least one of the rotator and the supporter swells with the target liquid. The second clearance may be a larger one of the inner clearance and the outer clearance in the state where the rotator and the supporter are not swelled with the target liquid.