A method for diagnosing a quality of a manufacturing facility with a plurality of production elements, the method comprising: continuously obtaining inspection values for a target product produced by the manufacturing facility; deriving a conversion peak per frequency indicating a degree of expression per production cycle by separating the inspection values for each frequency band; securing a natural frequency for each production element expressed per production cycle for each production element; and diagnosing a quality of each production element by comparing the natural frequency of each production element and a conversion peak per frequency, wherein the each production element is an equipment element that is involved in the production of the target product; wherein the equipment element is an electrochemical device manufacturing equipment element; wherein the continuously obtaining the inspection values for the target product includes inspecting a specific element of the target product and continuously acquiring the inspection values by comparing inspection results based on a reference value; Auxiliary request wherein the securing the natural frequency for each production element expressed per production cycle for each production element includes deriving the each production element that affects a production of the target product, and securing the natural frequency based on a number of expressions per production cycle for each production element; and wherein the number of expressions per production cycle for each production element is a result of extracting a frequency at which an inspection value for a specific element of the target product deviates from a standard value due to an influence of the each production element. continuously obtaining inspection values for a target product produced by the manufacturing facility; deriving a conversion peak per frequency indicating a degree of expression per production cycle by separating the inspection values for each frequency band; securing a natural frequency for each production element expressed per production cycle for each production element; and diagnosing a quality of each production element by comparing the natural frequency of each production element and a conversion peak per frequency, wherein the each production element is an equipment element that is involved in the production of the target product; wherein the equipment element is an electrochemical device manufacturing equipment element; wherein the continuously obtaining the inspection values for the target product includes inspecting a specific element of the target product and continuously acquiring the inspection values by comparing inspection results based on a reference value; wherein the securing the natural frequency for each production element expressed per production cycle for each production element includes deriving the each production element that affects a production of the target product, and securing the natural frequency based on a number of expressions per production cycle for each production element; and wherein the number of expressions per production cycle for each production element is a result of extracting a frequency at which an inspection value for a specific element of the target product deviates from a standard value due to an influence of the each production element. <EOS>