A battery residual amount measurement system including includes a current detection section that detects a current value of current discharged from a battery that is an object of measurement; a first storage section that stores reference undischargeable amounts that are determined in advance in accordance with ambient temperatures of the battery and current values of current discharged from the battery; and a calculating section that, when a discharging operation is carried out at the battery, acquires, from the first storage section, the reference undischargeable amount that corresponds to an ambient temperature of the battery and the current value detected by the current detection section, and calculates a battery residual amount on the basis of a undischargeable amount that is calculated and computed on the basis of the acquired reference undischargeable amount and a nominal battery capacity of the battery.