A battery state estimating device comprising: a current detecting part configured to detect a current flowing through a secondary battery as a measured current value; a voltage detecting part configured to detect a terminal voltage of the secondary battery as a measured voltage value; an identification calculation part (304, 305) configured to obtain transformed state amounts by subjecting the measured current value and the measured voltage value to filter processing using a state variable filter and thus estimate a terminal voltage of the secondary battery which is based on the obtained stage amounts and a battery model of the secondary battery, wherein the terminal voltage is a model output of the battery model, as an estimated voltage value on the basis of the transformed state amounts and identified parameters of the battery model defined as shown in Formula where the measured voltage value is V, the measured current value is I, s is a differential operator, and A(s) and B(s) are polynomial functions of the differential operator s, and perform sequential identification calculation of sequentially identifying the parameters of the battery model, which composes a parameter vector including multiple parameters in such a way that a difference between a value based on the measured voltage value and the estimated voltage value converges to zero; characterized in that a limit processing part configured to determine whether, among the parameters identified by the identification calculation part (304, 305), a highest-degree term parameter included in a coefficient of a term with the highest degree in a polynomial s·(s) of the Formula is equal to or larger than a predetermined first threshold, and perform upper limit processing of setting a value of the highest-degree term parameter to the first threshold when the highest-degree term parameter is equal to or larger than the first threshold. [Formula 17] V = B s s ⋅ A s ⋅ I a current detecting part configured to detect a current flowing through a secondary battery as a measured current value; a voltage detecting part configured to detect a terminal voltage of the secondary battery as a measured voltage value; an identification calculation part (304, 305) configured to obtain transformed state amounts by subjecting the measured current value and the measured voltage value to filter processing using a state variable filter and thus estimate a terminal voltage of the secondary battery which is based on the obtained stage amounts and a battery model of the secondary battery, wherein the terminal voltage is a model output of the battery model, as an estimated voltage value on the basis of the transformed state amounts and identified parameters of the battery model defined as shown in Formula where the measured voltage value is V, the measured current value is I, s is a differential operator, and A(s) and B(s) are polynomial functions of the differential operator s, and perform sequential identification calculation of sequentially identifying the parameters of the battery model, which composes a parameter vector including multiple parameters in such a way that a difference between a value based on the measured voltage value and the estimated voltage value converges to zero; obtain transformed state amounts by subjecting the measured current value and the measured voltage value to filter processing using a state variable filter and thus estimate a terminal voltage of the secondary battery which is based on the obtained stage amounts and a battery model of the secondary battery, wherein the terminal voltage is a model output of the battery model, as an estimated voltage value on the basis of the transformed state amounts and identified parameters of the battery model defined as shown in Formula where the measured voltage value is V, the measured current value is I, s is a differential operator, and A(s) and B(s) are polynomial functions of the differential operator s, and perform sequential identification calculation of sequentially identifying the parameters of the battery model, which composes a parameter vector including multiple parameters in such a way that a difference between a value based on the measured voltage value and the estimated voltage value converges to zero; characterized in that a limit processing part configured to determine whether, among the parameters identified by the identification calculation part (304, 305), a highest-degree term parameter included in a coefficient of a term with the highest degree in a polynomial s·(s) of the Formula is equal to or larger than a predetermined first threshold, and perform upper limit processing of setting a value of the highest-degree term parameter to the first threshold when the highest-degree term parameter is equal to or larger than the first threshold. [Formula 17] V = B s s ⋅ A s ⋅ I determine whether, among the parameters identified by the identification calculation part (304, 305), a highest-degree term parameter included in a coefficient of a term with the highest degree in a polynomial s·(s) of the Formula is equal to or larger than a predetermined first threshold, and perform upper limit processing of setting a value of the highest-degree term parameter to the first threshold when the highest-degree term parameter is equal to or larger than the first threshold. [Formula 17] V = B s s ⋅ A s ⋅ I