A battery status estimation apparatus coupled to an assembled battery with a plurality of serially-connected cells and for setting any one of the plurality of cells as a target cell and estimating a state of charge, SOC, of the target cell, the battery status estimation apparatus comprising: a cell voltage acquisition unit that acquires a measurement result of a closed circuit voltage, CCV, of the target cell; a reference cell information acquisition unit that sets a reference cell with respect to the plurality of cells and acquires a closed circuit voltage, CCV, and an open circuit voltage, OCV, of the reference cell and a reference SOC value, SOCave, representing a state of charge, SOC, of the reference cell; a temporary SOC operation unit that finds a temporary SOC value, SOCnx, representing a temporary state of charge of the target cell on the basis of the closed circuit voltage, CCV, of the target cell and the closed circuit voltage, CCV, and the open circuit voltage, OCV, of the reference cell; and an SOC operation unit that finds an SOC value representing the state of charge, SOC, of the target cell by using a result of smoothing processing executed on a difference between the temporary SOC value, SOCnx, and the reference SOC value, SOCave. the battery status estimation apparatus comprising: a cell voltage acquisition unit that acquires a measurement result of a closed circuit voltage, CCV, of the target cell; a reference cell information acquisition unit that sets a reference cell with respect to the plurality of cells and acquires a closed circuit voltage, CCV, and an open circuit voltage, OCV, of the reference cell and a reference SOC value, SOCave, representing a state of charge, SOC, of the reference cell; a temporary SOC operation unit that finds a temporary SOC value, SOCnx, representing a temporary state of charge of the target cell on the basis of the closed circuit voltage, CCV, of the target cell and the closed circuit voltage, CCV, and the open circuit voltage, OCV, of the reference cell; and an SOC operation unit that finds an SOC value representing the state of charge, SOC, of the target cell by using a result of smoothing processing executed on a difference between the temporary SOC value, SOCnx, and the reference SOC value, SOCave. a cell voltage acquisition unit that acquires a measurement result of a closed circuit voltage, CCV, of the target cell; a reference cell information acquisition unit that sets a reference cell with respect to the plurality of cells and acquires a closed circuit voltage, CCV, and an open circuit voltage, OCV, of the reference cell and a reference SOC value, SOCave, representing a state of charge, SOC, of the reference cell; a temporary SOC operation unit that finds a temporary SOC value, SOCnx, representing a temporary state of charge of the target cell on the basis of the closed circuit voltage, CCV, of the target cell and the closed circuit voltage, CCV, and the open circuit voltage, OCV, of the reference cell; and an SOC operation unit that finds an SOC value representing the state of charge, SOC, of the target cell by using a result of smoothing processing executed on a difference between the temporary SOC value, SOCnx, and the reference SOC value, SOCave.