Filling level meter (4) for membrane gasometer (1), including at least one accumulation chamber (C1) arranged for containing a gas, and an impermeable flexible membrane (2) capable of moving between two positions corresponding to the chamber being totally full and totally empty, wherein the meter (4) includes: an instrument (12) associated with a fixed element (3, 9), arranged for generating a signal of measurement of a physical value that can be correlated to the quantity of gas contained in the chamber (C1); elements for processing and displaying (5) the value of the quantity of gas corresponding to the generated signal; a filiform, flexible element (6) for connecting the instrument (12) and the membrane (2); the filiform, flexible element (6) including at least one portion constituted by an elastic member (7).