NOVELTY - The device (101) has an M-sequence-signal-generating unit (111) that generates a binary or more M-sequence signal with a white power spectrum. A superimposed-signal-generating unit (112) generates a superimposed signal superimposed on M-sequence signal. An impedance calculator (106) calculates impedance of fuel cell, based on values of current and voltage measured by current and voltage measuring unit (107). The signal after the application in second signal-adding unit (104) is output to control the battery and the calculation result is output as a measured result.    USE - Device for measuring sequential impedance of fuel cell in control system of fuel cell system (claimed) in fuel cell electric vehicles (FCEV).    ADVANTAGE - The impedance of fuel cell can be determined appropriately. Quick measurement can be carried out with high precision and in broad frequency range while applying a signal having a power output fluctuation similar to that of normal operation device. The phenomena which occur in different frequency ranges can be determined simultaneously.    DETAILED DESCRIPTION - A signal-processing section combines M-sequence signal and superimposed signal or separately outputs the M-sequence signal or superimposed signal. A first signal-adding unit (103) superimposes and applies a signal output from the signal-processing section on the power indication value or the current indication value, where the values are sent by the control processor. A second signal-adding unit superimposes and applies a signal inverted from the signal output from the signal-processing section on the power indication value or the current indication value, where the values are sent by the control processor. A current and voltage measuring unit (107) measures and incorporates a current and a voltage of the fuel cell which is controlled by a signal generated by the first signal-adding unit. INDEPENDENT CLAIMS are included for the following:    (1) a method for measuring sequential impedance of fuel cell in control system; and    (2) a fuel cell system.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the configuration of sequential impedance measurement device in fuel cell vehicle.    Device for measuring sequential impedance of fuel cell (101)    Signal-adding units (103,104)    Impedance calculator (106)    Current and voltage measuring unit (107)    M-sequence-signal-generating unit (111)    Superimposed-signal-generating unit (112)