Abstract: A method and device of measuring a water level of a frequency analysis type is disclosed. The device is consisted of a pipe type of which immersed length is in a proportion to the water level and which is installed in a container having a fluid, a signal detecting device which has an impact apparatus to provide a source signal periodically or continuously and a impact detecting sensor(s) which gets a response signal of the pipe by the impact apparatus, and a signal analyzer which processes the signal from the impact detecting sensor. The method comprises steps of: generating a source signal to the pipe by the impact apparatus; detecting the response signal of the pipe according the water level by the impact detecting sensor; analyzing the response signal to the frequency response spectra by the signal analyzer; and measuring the water level by comparing to the predetermined frequencies which was obtained by the signal analyzer.