A laminated battery, comprising: an alternating-current power supply unit (71,72) connected to an internal resistance measurement object including at least the laminated battery, unit cells being laminated in the laminated battery, and configured to output an alternating current to the internal resistance measurement object; an alternating current adjustment unit configured to adjust the alternating current such that a positive-electrode side alternating-current potential difference between a potential (Vc) on a positive electrode side of the internal resistance measurement object and a potential (Vm) of an intermediate part matches a negative electrode side alternating-current potential difference between a potential (Va) on a negative-electrode side of the internal resistance measurement object and the potential (Vm) of the intermediate part; and a calculation unit configured to calculate an internal resistance of the laminated battery on the basis of the adjusted alternating current and alternating-current potential differences; wherein: the unit cell includes: a separator (3,4); and a membrane electrode assembly forming a power generation region; and the separator (3,4) includes: a source connection point tab for inputting and outputting the alternating current from the alternating current adjustment unit; and a sense connection point tab for detecting a potential of the alternating current that is input and output through the source connection point tab, characterized in that: the sense connection point tab and the source connection point tab are arranged at the same lateral side of the power generation region and the source connection point tab is arranged at a position closer to the power generation region than the sense connection point tab; or the source connection point tab and the sense connection point tab are arranged at positions facing each other across the power generation region; or the source connection point tab and the sense connection point tab are arranged at positions diagonal to each other across the power generation region. an alternating-current power supply unit (71,72) connected to an internal resistance measurement object including at least the laminated battery, unit cells being laminated in the laminated battery, and configured to output an alternating current to the internal resistance measurement object; an alternating current adjustment unit configured to adjust the alternating current such that a positive-electrode side alternating-current potential difference between a potential (Vc) on a positive electrode side of the internal resistance measurement object and a potential (Vm) of an intermediate part matches a negative electrode side alternating-current potential difference between a potential (Va) on a negative-electrode side of the internal resistance measurement object and the potential (Vm) of the intermediate part; and a calculation unit configured to calculate an internal resistance of the laminated battery on the basis of the adjusted alternating current and alternating-current potential differences; wherein: the unit cell includes: a separator (3,4); and a membrane electrode assembly forming a power generation region; and the separator (3,4) includes: a source connection point tab for inputting and outputting the alternating current from the alternating current adjustment unit; and a sense connection point tab for detecting a potential of the alternating current that is input and output through the source connection point tab, the unit cell includes: a separator (3,4); and a membrane electrode assembly forming a power generation region; and a separator (3,4); and a membrane electrode assembly forming a power generation region; and the separator (3,4) includes: a source connection point tab for inputting and outputting the alternating current from the alternating current adjustment unit; and a sense connection point tab for detecting a potential of the alternating current that is input and output through the source connection point tab, a source connection point tab for inputting and outputting the alternating current from the alternating current adjustment unit; and a sense connection point tab for detecting a potential of the alternating current that is input and output through the source connection point tab, characterized in that: the sense connection point tab and the source connection point tab are arranged at the same lateral side of the power generation region and the source connection point tab is arranged at a position closer to the power generation region than the sense connection point tab; or the source connection point tab and the sense connection point tab are arranged at positions facing each other across the power generation region; or the source connection point tab and the sense connection point tab are arranged at positions diagonal to each other across the power generation region. the sense connection point tab and the source connection point tab are arranged at the same lateral side of the power generation region and the source connection point tab is arranged at a position closer to the power generation region than the sense connection point tab; or the source connection point tab and the sense connection point tab are arranged at positions facing each other across the power generation region; or the source connection point tab and the sense connection point tab are arranged at positions diagonal to each other across the power generation region.