Provided is a secondary battery degradation determination device for an emergency power source in which a plurality of battery groups each having a plurality of batteries connected in series are connected in parallel, wherein the secondary battery degradation determination device is capable of accurately determining degradation of each battery, is simple and can be manufactured at low cost, and, in particular, allows a means for generating a measurement current containing an AC component to be simple and compact. The secondary battery degradation determination device includes: a plurality of voltage sensors (7) connected to respective batteries (2); a discharge circuit (9) connected in parallel to battery groups (3); and discharge control means (11e). The discharge control means (11e) drives a switching element (27) to be opened and closed so that a current flowing through the discharge circuit (9) has a pulse shape or the like. The voltage sensors (7) each measure a voltage value of an AC component. An internal resistance calculation unit calculates an internal resistance on the basis of the measured value, and a determination unit determines degradation of the batteries (2) on the basis of the internal resistance.