A diagnosis device for diagnosing a measurement state of a device configured to measure an impedance of a laminated battery, said diagnosis device comprising: a power supply unit (531,532) configured to output an alternating current for measuring an impedance of the laminated battery to a positive electrode and a negative electrode of the laminated battery, a plurality of battery cells being laminated in the laminated battery; a detection unit (521,522) configured to detect at least one of an alternating-current potential difference between the positive electrode and an intermediate point of the laminated battery and an alternating-current potential difference between the negative electrode and the intermediate point; a computation unit configured to compute the impedance of the laminated battery on the basis of the alternating-current potential difference detected by the detection unit (521,522) and the alternating current output from the power supply unit (531,532); and a diagnosis element (561,562) having a predetermined impedance reference value and necessary to calculate a measurement error of the impedance, characterized by a switch unit configured to alternately switch a battery connection state for connecting the power supply unit (531,532) and the detection unit (521,522) to the laminated battery and a diagnosis element connection state for cutting off connection to the laminated battery and connecting the power supply unit (531,532) and the detection unit (521,522) to the diagnosis element (561,562), wherein the computation unit is adapted to, when the switch unit is switched to the diagnosis element connection state, measure an impedance of the diagnosis element, calculate a difference between a measurement value of the impedance of the diagnosis element and the impedance reference value as a measurement error and diagnose a measurement state of the device on the basis of the measurement error. a power supply unit (531,532) configured to output an alternating current for measuring an impedance of the laminated battery to a positive electrode and a negative electrode of the laminated battery, a plurality of battery cells being laminated in the laminated battery; a detection unit (521,522) configured to detect at least one of an alternating-current potential difference between the positive electrode and an intermediate point of the laminated battery and an alternating-current potential difference between the negative electrode and the intermediate point; a computation unit configured to compute the impedance of the laminated battery on the basis of the alternating-current potential difference detected by the detection unit (521,522) and the alternating current output from the power supply unit (531,532); and a diagnosis element (561,562) having a predetermined impedance reference value and necessary to calculate a measurement error of the impedance, characterized by a switch unit configured to alternately switch a battery connection state for connecting the power supply unit (531,532) and the detection unit (521,522) to the laminated battery and a diagnosis element connection state for cutting off connection to the laminated battery and connecting the power supply unit (531,532) and the detection unit (521,522) to the diagnosis element (561,562), wherein the computation unit is adapted to, when the switch unit is switched to the diagnosis element connection state, measure an impedance of the diagnosis element, calculate a difference between a measurement value of the impedance of the diagnosis element and the impedance reference value as a measurement error and diagnose a measurement state of the device on the basis of the measurement error.