An estimation device 4 is provided with: an acquisition unit 41 for acquiring time-series data about an SOC of a power storage element; a specification unit 41 for specifying a fluctuation range of the SOC in the time-series data and an SOC representative value representing an SOC region in the fluctuation range; and an estimation unit 41 for estimating a shape change of the power storage element on the basis of the specified fluctuation range and the specified representative value.