A battery management apparatus comprising: a state of charge SOC calculation unit configured to calculate an SOC for each of a plurality of battery modules by using at least one of voltage, current, or temperature measured for the battery module in which a plurality of battery cells are connected in parallel; a state of health SOH calculation unit configured to calculate an SOH for each of the battery modules based on the SOC calculated by the SOC calculation unit and at least one of the voltage, current, and temperature of the battery module; and a diagnosis unit configured to calculate a SOH change rate using the SOH, and diagnose a state of the battery module using the calculated SOH change rate, wherein the state of the battery module is any one of a normal state, a state including a degenerate battery cell, and a state including a current interrupt device CID open battery cell, characterized in that: the diagnosis unit is configured to diagnose the state of the battery modules by comparing the SOH change rate of each of the plurality of battery modules, wherein the diagnosis unit is configured to: diagnose the battery module as the state including a degenerate battery cell, if the SOH change rate of the battery module is greater than a first preset value and less than a second preset value compared to the SOH change rate of other battery modules during a predetermined time, diagnose the battery module as the state including a CID open battery cell, if the SOH reduction rate of the battery module is (1/number of battery cells in the battery module) * 100% or more during the predetermined time, diagnose the battery module as the normal state, if it is not in the state including the degenerate battery cell or including the CID open battery cell. a state of charge SOC calculation unit configured to calculate an SOC for each of a plurality of battery modules by using at least one of voltage, current, or temperature measured for the battery module in which a plurality of battery cells are connected in parallel; a state of health SOH calculation unit configured to calculate an SOH for each of the battery modules based on the SOC calculated by the SOC calculation unit and at least one of the voltage, current, and temperature of the battery module; and a diagnosis unit configured to calculate a SOH change rate using the SOH, and diagnose a state of the battery module using the calculated SOH change rate, wherein the state of the battery module is any one of a normal state, a state including a degenerate battery cell, and a state including a current interrupt device CID open battery cell, characterized in that: the diagnosis unit is configured to diagnose the state of the battery modules by comparing the SOH change rate of each of the plurality of battery modules, wherein the diagnosis unit is configured to: diagnose the battery module as the state including a degenerate battery cell, if the SOH change rate of the battery module is greater than a first preset value and less than a second preset value compared to the SOH change rate of other battery modules during a predetermined time, diagnose the battery module as the state including a CID open battery cell, if the SOH reduction rate of the battery module is (1/number of battery cells in the battery module) * 100% or more during the predetermined time, diagnose the battery module as the normal state, if it is not in the state including the degenerate battery cell or including the CID open battery cell. diagnose the battery module as the state including a degenerate battery cell, if the SOH change rate of the battery module is greater than a first preset value and less than a second preset value compared to the SOH change rate of other battery modules during a predetermined time, diagnose the battery module as the state including a CID open battery cell, if the SOH reduction rate of the battery module is (1/number of battery cells in the battery module) * 100% or more during the predetermined time, diagnose the battery module as the normal state, if it is not in the state including the degenerate battery cell or including the CID open battery cell.