An electric power distribution system which is mounted on a vehicle, and configured to supply electric power to a backup load (6_2) from a second DC/DC converter (1_2) and a second battery (7_2) provided in parallel with the second DC/DC converter (1_2), the electric power distribution system comprising: a first path through which electric power is supplied from at least one of a first DC/DC converter (1_1) and a first battery (7_1) to a main load (6_1), wherein the the first DC/DC converter (1_1) is a converter other than the second DC/DC converter (1_2), the first battery (7_1) is a battery other than the second battery (7_2), and the main load (6_1) is a load other than the backup load (6_2); a second path that is provided in parallel with the first path and through which electric power is supplied from at least one of the second DC/DC converter (1_2) and the second battery (7_2) to the backup load (6_2); a third path that connects the second DC/DC converter (1_2) and the first battery (7_1); a fourth path that connects the first path and the third path and connects the first battery (7_1) and the first DC/DC converter (1_1) in parallel to the main load (6_1); and characterized in that the electric power distribution system is configured to supply electric power to the main load (6_1) from the first DC/DC converter (1_1) and the first battery (7_1) provided in parallel with the first DC/DC converter (1_1), and the electric power distribution system comprises a control unit that is configured to control an output voltage of the second DC/DC converter (1_2) according to a charge amount target value of the second battery (7_2), which is derived from travel route information of a navigation system mounted on the vehicle, wherein the charge amount target value is: - sufficient to supply electric power to the backup load (6_2) to reach a midway point (a1, a2) of a moving distance of the vehicle from a current point to a target point, and - set to be lower than a threshold battery capacity that is lower than in a fully charged state of the second battery (7_2). is mounted on a vehicle, and configured to supply electric power to a backup load (6_2) from a second DC/DC converter (1_2) and a second battery (7_2) provided in parallel with the second DC/DC converter (1_2), the electric power distribution system comprising: a first path through which electric power is supplied from at least one of a first DC/DC converter (1_1) and a first battery (7_1) to a main load (6_1), wherein the the first DC/DC converter (1_1) is a converter other than the second DC/DC converter (1_2), the first battery (7_1) is a battery other than the second battery (7_2), and the main load (6_1) is a load other than the backup load (6_2); a first path through which electric power is supplied from at least one of a first DC/DC converter (1_1) and a first battery (7_1) to a main load (6_1), wherein the the first DC/DC converter (1_1) is a converter other than the second DC/DC converter (1_2), the first battery (7_1) is a battery other than the second battery (7_2), and the main load (6_1) is a load other than the backup load (6_2); a second path that is provided in parallel with the first path and through which electric power is supplied from at least one of the second DC/DC converter (1_2) and the second battery (7_2) to the backup load (6_2); a third path that connects the second DC/DC converter (1_2) and the first battery (7_1); a fourth path that connects the first path and the third path and connects the first battery (7_1) and the first DC/DC converter (1_1) in parallel to the main load (6_1); and characterized in that the electric power distribution system is configured to supply electric power to the main load (6_1) from the first DC/DC converter (1_1) and the first battery (7_1) provided in parallel with the first DC/DC converter (1_1), and the electric power distribution system comprises a control unit that is configured to control an output voltage of the second DC/DC converter (1_2) according to a charge amount target value of the second battery (7_2), which is derived from travel route information of a navigation system mounted on the vehicle, wherein the charge amount target value is: - sufficient to supply electric power to the backup load (6_2) to reach a midway point (a1, a2) of a moving distance of the vehicle from a current point to a target point, and - set to be lower than a threshold battery capacity that is lower than in a fully charged state of the second battery (7_2). - sufficient to supply electric power to the backup load (6_2) to reach a midway point (a1, a2) of a moving distance of the vehicle from a current point to a target point, and - set to be lower than a threshold battery capacity that is lower than in a fully charged state of the second battery (7_2).