It is difficult to know the remaining amount and the degradation state of a power storage device, and it is also difficult to estimate how long the power storage device can be used. Data obtained through midway discharge and mid-to-full charge is used as the learning data to calculate the degradation state and the capacity. In other words, the learning data includes both a discharge curve of midway discharge and a charge curve of mid-to-full charge, and neural network processing is performed with the use of the learned data.