A control device for a hybrid vehicle, comprising: a motor generator mechanically connected to an output shaft of an engine; a first battery electrically connected to the motor generator; a second battery electrically connected to an electric load of the vehicle; first and second relays (43a, 43b) that are able to electrically connect the first battery to the second battery by turning at least one of the relays (43a, 43b) on or off; a motor generator control unit adapted to cause the motor generator to carry out a power operation or a regenerative operation in accordance with an operation state of the vehicle; a relay control unit adapted to turn off first and second relays (43a, 43b) during the power operation of the motor generator so as to disconnect an electric connection between the first battery and the second battery, the relay control unit also adapted to turn on one relay of the first and second relays (43a, 43b) during the regenerative operation of the motor generator so as to electrically connect the first battery to the second battery; and an engine control unit, which comprises: voltage detecting means for detecting a voltage of the first battery respectively of the second battery; and an on-fixation failure detecting unit adapted to detect an on-fixation failure in which the relay (43a, 43b) is fixed in an on state on the basis of the voltage of the second battery during power operation of the motor generator when the first relay and the second relay are commanded to be turned-off; and an off-fixation failure detecting unit adapted to detect an off-fixation failure in which one of the relays (43a, 43b) is fixed in an off state on the basis of difference between the voltage of the first battery and the voltage of the second battery during the regenerative operation of the motor generator when the first relay and the second relay are commanded to be turned-on; wherein the motor generator control unit prohibits the power operation of the motor generator in a case where either the on-fixation failure or the off-fixation failure of any of the first and the second relays (43a, 43b) is detected. a motor generator mechanically connected to an output shaft of an engine; a first battery electrically connected to the motor generator; a second battery electrically connected to an electric load of the vehicle; first and second relays (43a, 43b) that are able to electrically connect the first battery to the second battery by turning at least one of the relays (43a, 43b) on or off; a motor generator control unit adapted to cause the motor generator to carry out a power operation or a regenerative operation in accordance with an operation state of the vehicle; a relay control unit adapted to turn off first and second relays (43a, 43b) during the power operation of the motor generator so as to disconnect an electric connection between the first battery and the second battery, the relay control unit also adapted to turn on one relay of the first and second relays (43a, 43b) during the regenerative operation of the motor generator so as to electrically connect the first battery to the second battery; and an engine control unit, which comprises: voltage detecting means for detecting a voltage of the first battery respectively of the second battery; and an on-fixation failure detecting unit adapted to detect an on-fixation failure in which the relay (43a, 43b) is fixed in an on state on the basis of the voltage of the second battery during power operation of the motor generator when the first relay and the second relay are commanded to be turned-off; and an off-fixation failure detecting unit adapted to detect an off-fixation failure in which one of the relays (43a, 43b) is fixed in an off state on the basis of difference between the voltage of the first battery and the voltage of the second battery during the regenerative operation of the motor generator when the first relay and the second relay are commanded to be turned-on; wherein the motor generator control unit prohibits the power operation of the motor generator in a case where either the on-fixation failure or the off-fixation failure of any of the first and the second relays (43a, 43b) is detected. voltage detecting means for detecting a voltage of the first battery respectively of the second battery; and an on-fixation failure detecting unit adapted to detect an on-fixation failure in which the relay (43a, 43b) is fixed in an on state on the basis of the voltage of the second battery during power operation of the motor generator when the first relay and the second relay are commanded to be turned-off; and an off-fixation failure detecting unit adapted to detect an off-fixation failure in which one of the relays (43a, 43b) is fixed in an off state on the basis of difference between the voltage of the first battery and the voltage of the second battery during the regenerative operation of the motor generator when the first relay and the second relay are commanded to be turned-on; wherein the motor generator control unit prohibits the power operation of the motor generator in a case where either the on-fixation failure or the off-fixation failure of any of the first and the second relays (43a, 43b) is detected.