A vehicle comprises a battery, i.e. a power storage unit having a capacity different from a reference capacity, a current sensor for detecting a current inputted to the power storage unit or outputted therefrom and delivering the detection value by converting it depending on the ratio of the capacity of the power storage unit to the reference capacity, and a controller performing current integration by receiving the output from the current detecting section and judging charged state of the power storage unit. The current sensor preferably comprises a sensor for measuring a current flowing through wiring connected with the power storage unit, and a converting section for converting the sensor output depending on the ratio of the capacity of the power storage unit to the reference capacity. When the capacity of the power storage unit is equal to n times of the reference capacity, the converting section delivers the sensor output while multiplying by 1/n.