To reduce calculation errors of remaining batter power so as to take into account capacity diminutions due to cycle degradation and temperature, a remaining power calculation device specifies a temperature correction value for calculation of remaining battery power corresponding to temperature, from among temperature correction values changed every predetermined number of charge/discharge cycles stored in a correction value storage device, on the basis of a temperature of a battery cell measured by a temperature measurement device and the number of charge/discharge cycles counted by a charge/discharge counting device, and calculates remaining battery power corresponding to the specified temperature correction value. Temperature correction values changed every predetermined number of charge/discharge cycles are used instead of setting different temperature correction values for all charge/discharge cycles, whereby correction of remaining battery power based on cycle degradation and temperature is performed with a small number of parameters.