A charging/discharging control system for a hybrid vehicle including an internal combustion engine and a motor each serving as a motive power source, and a power storage device configured to be capable of receiving and supplying electric power from and to said motor, the charging/discharging control system comprising: an externally charging unit configured to charge said power storage device using an electric power source external to the vehicle; an electric power generating unit configured to generate electric power for charging said power storage device, using an output of said internal combustion engine; a charge state estimating unit configured to estimate a remaining level in said power storage device based on a state detection value of said power storage device; a traveling control unit for controlling operations of said internal combustion engine and said motor; said traveling control unit including a traveling mode selecting unit configured to select a second traveling mode until said remaining level estimated value is decreased to reach a mode determination value, and select a first traveling mode once said remaining level estimated value is decreased to reach said mode determination value, in said second traveling mode, said internal combustion engine and said motor being used to travel mainly using said motor with said internal charging being stopped; the charging/discharging control system being characterized in that: said traveling control unit is configured so as to encourage internal charging using said electric power generating unit when a remaining level estimated value obtained from said charge state estimating unit is decreased to fall below a control target during a vehicle operation in said first traveling mode, in which said internal combustion engine and said motor are used to maintain the remaining level of said power storage device within a predetermined control range; a malfunction detecting unit configured to detect a malfunction associated with said power storage device; and a malfunction processing unit configured to set said control target at a value higher than that employed when no malfunction is detected, when said malfunction detecting unit detects the malfunction, said malfunction processing unit being configured to set said mode determination value at a value higher than that employed when no malfunction is detected, when said malfunction is detected during the vehicle operation in said second traveling mode. an externally charging unit configured to charge said power storage device using an electric power source external to the vehicle; an electric power generating unit configured to generate electric power for charging said power storage device, using an output of said internal combustion engine; a charge state estimating unit configured to estimate a remaining level in said power storage device based on a state detection value of said power storage device; a traveling control unit for controlling operations of said internal combustion engine and said motor; said traveling control unit including a traveling mode selecting unit configured to select a second traveling mode until said remaining level estimated value is decreased to reach a mode determination value, and select a first traveling mode once said remaining level estimated value is decreased to reach said mode determination value, in said second traveling mode, said internal combustion engine and said motor being used to travel mainly using said motor with said internal charging being stopped; the charging/discharging control system being characterized in that: said traveling control unit is configured so as to encourage internal charging using said electric power generating unit when a remaining level estimated value obtained from said charge state estimating unit is decreased to fall below a control target during a vehicle operation in said first traveling mode, in which said internal combustion engine and said motor are used to maintain the remaining level of said power storage device within a predetermined control range; a malfunction detecting unit configured to detect a malfunction associated with said power storage device; and a malfunction processing unit configured to set said control target at a value higher than that employed when no malfunction is detected, when said malfunction detecting unit detects the malfunction, said malfunction processing unit being configured to set said mode determination value at a value higher than that employed when no malfunction is detected, when said malfunction is detected during the vehicle operation in said second traveling mode. said traveling control unit is configured so as to encourage internal charging using said electric power generating unit when a remaining level estimated value obtained from said charge state estimating unit is decreased to fall below a control target during a vehicle operation in said first traveling mode, in which said internal combustion engine and said motor are used to maintain the remaining level of said power storage device within a predetermined control range; a malfunction detecting unit configured to detect a malfunction associated with said power storage device; and a malfunction processing unit configured to set said control target at a value higher than that employed when no malfunction is detected, when said malfunction detecting unit detects the malfunction, said malfunction processing unit being configured to set said mode determination value at a value higher than that employed when no malfunction is detected, when said malfunction is detected during the vehicle operation in said second traveling mode.