A battery management system comprising: a plurality of field devices (20A, 20B, 20C) of a battery-driven type, the plurality of field devices (20A, 20B, 20C) being associated with a facility disposed in a plant and being defined as belonging to a same group; and a battery management device configured to manage the plurality of field devices (20A, 20B, 20C), characterized in that it comprises: a battery manager configured to, in a case where the battery manager (101 is configured to receive battery life information representing that an amount of consumption of an installed battery (221A, 221B, 221C) is larger than an amount of consumption set advance, from a first field device that is one field device currently operating among the plurality of field devices (20A, 20B, 20C), switch the operating field device to a second field device that is another field device belonging to the same group and of which operation was stopped, wherein in a case where the battery manager receives the battery life information from the first field device, and the battery manager receives, from the second field device being configured to be operated at predetermined time intervals, battery remaining amount information representing a remaining amount of an installed battery (221A, 221B, 221C) in the second field device, then, the battery manager is configured to: transmit, to the second field device that has transmitted the battery remaining amount information representing the remaining amount higher than a predetermined value, operation control information instructing to perform a normal operation;transmit, to the first field device, operation control information used for causing the first field device to delete tag information representing a field device to perform a normal operation; transmit, to the second field device, operation control information used for setting the tag information; and transmit, to the first field device, operation control information used for controlling the first field device to stop the operation. a plurality of field devices (20A, 20B, 20C) of a battery-driven type, the plurality of field devices (20A, 20B, 20C) being associated with a facility disposed in a plant and being defined as belonging to a same group; and a battery management device configured to manage the plurality of field devices (20A, 20B, 20C), characterized in that it comprises: a battery manager configured to, in a case where the battery manager (101 is configured to receive battery life information representing that an amount of consumption of an installed battery (221A, 221B, 221C) is larger than an amount of consumption set advance, from a first field device that is one field device currently operating among the plurality of field devices (20A, 20B, 20C), switch the operating field device to a second field device that is another field device belonging to the same group and of which operation was stopped, wherein in a case where the battery manager receives the battery life information from the first field device, and the battery manager receives, from the second field device being configured to be operated at predetermined time intervals, battery remaining amount information representing a remaining amount of an installed battery (221A, 221B, 221C) in the second field device, then, the battery manager is configured to: transmit, to the second field device that has transmitted the battery remaining amount information representing the remaining amount higher than a predetermined value, operation control information instructing to perform a normal operation;transmit, to the first field device, operation control information used for causing the first field device to delete tag information representing a field device to perform a normal operation; transmit, to the second field device, operation control information used for setting the tag information; and transmit, to the first field device, operation control information used for controlling the first field device to stop the operation. transmit, to the second field device that has transmitted the battery remaining amount information representing the remaining amount higher than a predetermined value, operation control information instructing to perform a normal operation;transmit, to the first field device, operation control information used for causing the first field device to delete tag information representing a field device to perform a normal operation; transmit, to the second field device, operation control information used for setting the tag information; and transmit, to the first field device, operation control information used for controlling the first field device to stop the operation.