A charge-discharge control system that is applied to a vehicle including a battery and an electric power supply device , the battery being configured to supply electric power to an electrically-powered device , the electric power supply device being configured to supply electric power to the battery and the electrically-powered device , the charge-discharge control system being configured to adjust an amount of electric power charged to or discharged from the battery , the charge-discharge control system comprising an electronic control unit configured to: calculate a full charge capacity (SOCmax) of the battery ; calculate an excess or shortage of a state of charge (SOC) of the battery to a target state of charge of the state of charge (SOC) as a state-of-charge difference (ΔSOC), increase an output voltage of the electric power supply device when the shortage of the state of charge (SOC) is larger than a first prescribed value based on the state-of-charge difference (ΔSOC), and decrease the output voltage of the electric power supply device when the excess of the state of charge (SOC) is larger than a second prescribed value based on the state-of-charge difference (ΔSOC), calculate an amount of change (ΔVout) in the output voltage of the electric power supply device per unit time such that the amount of change (ΔVout) in the output voltage of the electric power supply device per unit time is smaller when the full charge capacity (SOCmax) is low than when the full charge capacity (SOCmax) is high, calculate a target voltage (Vn) of the output voltage of the electric power supply device by adding the amount of change (ΔVout) in the output voltage of the electric power supply device to a target voltage calculated in a last control cycle, and output an operation signal (MSdc) commensurate with the calculated target voltage (Vn) to the electric power supply device . calculate a full charge capacity (SOCmax) of the battery ; calculate an excess or shortage of a state of charge (SOC) of the battery to a target state of charge of the state of charge (SOC) as a state-of-charge difference (ΔSOC), increase an output voltage of the electric power supply device when the shortage of the state of charge (SOC) is larger than a first prescribed value based on the state-of-charge difference (ΔSOC), and decrease the output voltage of the electric power supply device when the excess of the state of charge (SOC) is larger than a second prescribed value based on the state-of-charge difference (ΔSOC), calculate an amount of change (ΔVout) in the output voltage of the electric power supply device per unit time such that the amount of change (ΔVout) in the output voltage of the electric power supply device per unit time is smaller when the full charge capacity (SOCmax) is low than when the full charge capacity (SOCmax) is high, calculate a target voltage (Vn) of the output voltage of the electric power supply device by adding the amount of change (ΔVout) in the output voltage of the electric power supply device to a target voltage calculated in a last control cycle, and output an operation signal (MSdc) commensurate with the calculated target voltage (Vn) to the electric power supply device . <EOS>