A method for determining a state of health of an electrochemical device, of the fuel cell type, from at least one physico-chemical parameter modelling at least partly the physico-chemical behaviour of said electrochemical device, said method being characterised in that it includes the following steps of: - applying to said electrochemical device an input signal comprising a plurality of electric excitations, each excitation belonging to a determined excitation category selected from a set formed by a sequence of current or voltage sinusoidal disturbances, about a bias point of said electrochemical device, the amplitude of disturbances being lower than 10% of a value of current at said bias point such that the response of the electrochemical device remains linear, each disturbance having a different frequency belonging to a main progression of frequencies, said sequence of disturbances being applied so as to alternately scan a plurality of sub-progressions (A 1,..., A n), each of said sub-progressions (A 1,..., A n) being a set of frequencies from the main progression, each sub-progression of said plurality being interleaved with at least one other sub-progression of the same plurality so that it includes at least one frequency included between two consecutive frequencies of said at least one sub-progression with which it is interleaved; a current or voltage step; and a current or voltage variation ranging from zero to a nominal value, said input signal comprising at least two excitations of different categories at least one of which being said sequence of current or voltage sinusoidal disturbances, and measuring an output signal of said electrochemical device in response to said input signal; and then - extracting, from said output signal, the response signals associated with each of said electric excitations; and then - estimating at least one first parameter from an electric excitation belonging to a first category from said at least two excitations of different categories previously applied, and from the corresponding response signal, wherein said at least one first parameter can be different from or identical to said at least one physico-chemical parameter; - estimating said at least one physico-chemical parameter from an electric excitation belonging to a category distinct from the first from said at least two excitations of different categories previously applied, from the corresponding response signal and from said at least one first parameter previously estimated; - estimating said state of health of the electrochemical device as a deviation between the value previously estimated of said at least one physico-chemical parameter and a predetermined reference value. - applying to said electrochemical device an input signal comprising a plurality of electric excitations, each excitation belonging to a determined excitation category selected from a set formed by a sequence of current or voltage sinusoidal disturbances, about a bias point of said electrochemical device, the amplitude of disturbances being lower than 10% of a value of current at said bias point such that the response of the electrochemical device remains linear, each disturbance having a different frequency belonging to a main progression of frequencies, said sequence of disturbances being applied so as to alternately scan a plurality of sub-progressions (A 1,..., A n), each of said sub-progressions (A 1,..., A n) being a set of frequencies from the main progression, each sub-progression of said plurality being interleaved with at least one other sub-progression of the same plurality so that it includes at least one frequency included between two consecutive frequencies of said at least one sub-progression with which it is interleaved; a current or voltage step; and a current or voltage variation ranging from zero to a nominal value, said input signal comprising at least two excitations of different categories at least one of which being said sequence of current or voltage sinusoidal disturbances, and measuring an output signal of said electrochemical device in response to said input signal; and then - extracting, from said output signal, the response signals associated with each of said electric excitations; and then - estimating at least one first parameter from an electric excitation belonging to a first category from said at least two excitations of different categories previously applied, and from the corresponding response signal, wherein said at least one first parameter can be different from or identical to said at least one physico-chemical parameter; - estimating said at least one physico-chemical parameter from an electric excitation belonging to a category distinct from the first from said at least two excitations of different categories previously applied, from the corresponding response signal and from said at least one first parameter previously estimated; - estimating said state of health of the electrochemical device as a deviation between the value previously estimated of said at least one physico-chemical parameter and a predetermined reference value.