Abstract: To achieve a fluid level measurement instrument requiring no detecting pipe that can accurately measure over a long period of time a fluid level in a tank for storing therein fluid without having to use a detecting pipe for sampling the fluid from the tank. A balance tube 41 has no detecting pipes and a solenoid coil 45 is wound around an outside of the balance tube 41. A float 46 containing therein a magnetic material 47 is disposed inside the solenoid coil 45. A cover 59 formed, for example, of metal covers an outer surface of the float 46 to prevent entry of fluid and hydrogen from outside. The float 46 moves according to a fluid level in the balance tube 41, which results also in inductance of the solenoid coil 45 being changed. Measuring the inductance of the solenoid coil 45 allows the fluid level of the balance tube 41 to be measured without having to use the detecting pipe.