A degradation degree assessment device for a secondary battery is to assess a degree of degradation of a secondary battery and includes a battery characteristic acquisition unit, a capacity estimation unit, and an assessment unit. The battery characteristic acquisition unit acquires a battery characteristic relating to a voltage transition of the secondary battery in a predetermined voltage section. The assessment unit assesses the degree of degradation of the secondary battery based on the battery characteristic acquired by the battery characteristic acquisition unit or based on a battery characteristic-related value computed on the basis of the battery characteristic.