1. A device for estimating a secondary cell status comprising: voltage detection means for detecting a voltage of the secondary cell; and computation means for estimating the secondary cell status by use of a plurality of models, the means including comparing estimated voltage values acquired from the plurality of models with a voltage value detected by the voltage detection means, selecting a model exhibiting highest correlation between the estimated voltage value and the voltage value as an optimum model, and estimating the secondary cell status by optimizing a parameter used in the optimum model by use of the voltage value detected by the voltage detection means.