A backup battery control module configured to supply electric power from a main battery to a load required for causing a vehicle to travel and supply electric power from a backup battery to the load when electric power supply from the main battery to the load is cut off, the backup battery control module comprising: an open circuit voltage measurement unit configured to measure an open circuit voltage of the backup battery every first predetermined time in a state in which an ignition switch is off, to obtain a measured open circuit voltage; an already charged rate derivation unit configured to derive, when the ignition switch is off and based on the measured open circuit voltage, an already charged rate of the backup battery that has already been charged, the already charged rate being a percentage and being a ratio of a remaining capacity already present in the backup battery to a remaining capacity of the backup battery having a charging rate of 100%; an internal resistance measurement unit configured to measure an internal resistance of the backup battery at every second predetermined time in a state in which the ignition switch is off, to obtain a measured internal resistance; a deterioration degree derivation unit configured to derive, when the ignition switch is off, a deterioration degree of the backup battery based on the measured internal resistance; a target charging rate derivation unit configured to derive, in a state in which the ignition switch is on, a target charging rate based on the deterioration degree, the target charging rate being a ratio of a required remaining capacity of the backup battery required to continue the driving of the load to the remaining capacity of the backup battery having the charging rate of 100%, wherein the remaining capacity of the backup battery having the charging rate of 100% decreases as the deterioration degree of the backup battery increases compared to a backup battery having no deterioration, the target charging rate serving as a charging target based on the deterioration degree such that the required remaining capacity required for the load is secured in the backup battery even when the electric power supply from the main battery to the load is cut off; and a charging control unit configured to charge, in a state in which the ignition switch is on, the backup battery until the already charged rate reaches the target charging rate in a case in which it is determined that the already charged rate is smaller than the target charging rate, wherein the target charging rate is set to be larger as the deterioration degree is higher. an open circuit voltage measurement unit configured to measure an open circuit voltage of the backup battery every first predetermined time in a state in which an ignition switch is off, to obtain a measured open circuit voltage; an already charged rate derivation unit configured to derive, when the ignition switch is off and based on the measured open circuit voltage, an already charged rate of the backup battery that has already been charged, the already charged rate being a percentage and being a ratio of a remaining capacity already present in the backup battery to a remaining capacity of the backup battery having a charging rate of 100%; an internal resistance measurement unit configured to measure an internal resistance of the backup battery at every second predetermined time in a state in which the ignition switch is off, to obtain a measured internal resistance; a deterioration degree derivation unit configured to derive, when the ignition switch is off, a deterioration degree of the backup battery based on the measured internal resistance; a target charging rate derivation unit configured to derive, in a state in which the ignition switch is on, a target charging rate based on the deterioration degree, the target charging rate being a ratio of a required remaining capacity of the backup battery required to continue the driving of the load to the remaining capacity of the backup battery having the charging rate of 100%, wherein the remaining capacity of the backup battery having the charging rate of 100% decreases as the deterioration degree of the backup battery increases compared to a backup battery having no deterioration, the target charging rate serving as a charging target based on the deterioration degree such that the required remaining capacity required for the load is secured in the backup battery even when the electric power supply from the main battery to the load is cut off; and a charging control unit configured to charge, in a state in which the ignition switch is on, the backup battery until the already charged rate reaches the target charging rate in a case in which it is determined that the already charged rate is smaller than the target charging rate, wherein the target charging rate is set to be larger as the deterioration degree is higher.