A power storage apparatus including a battery and a control circuit that controls the charging or discharging of the battery, wherein during a polarization elimination time period extending from the charging/discharging end time of the battery to a polarization-eliminated time at which polarization of the battery can be judged to have been eliminated, the control circuit obtains, as an amount of change, the difference between a voltage measured at a first time set according to the temperature of the battery and a voltage measured at a second time following the first time and set according to the temperature of the battery, and sums the product of the amount of change and an estimation coefficient and the voltage measured at the first or second time so as to estimate an open-circuit voltage of the battery to be provided after elimination of the polarization of the battery.