A vehicle control device that controls operation of a vehicle, the vehicle control device comprising: first and second computing units (2, 3) that execute control computation for controlling the operation of the vehicle; a memory diagnosis unit that diagnoses a shared storage area shared by the first and second computing units (2, 3); characterized by: an auxiliary storage unit that stores a copy of data stored in an area to be diagnosed, the area being diagnosed by the memory diagnosis unit; and an access destination setting unit that sets an access destination address in such a manner that while the memory diagnosis unit diagnoses the area to be diagnosed, the first and second computing units (2, 3) execute the control computation by using the copy stored in the auxiliary storage unit as an alternative to the data stored in the area to be diagnosed, wherein the vehicle control device includes a shared storage device having the shared storage area, the auxiliary storage unit is configured as an auxiliary storage area for storing the copy, and the vehicle control device further includes an auxiliary storage device that is a storage device different from the shared storage device, and that has the auxiliary storage area, wherein the auxiliary storage device is configured by a storage device having a reliability higher than a reliability of the shared storage device, and wherein the auxiliary storage device is configured as a storage device having a reliability higher than a reliability of the shared storage device by being configured as an exclusive storage device in which while one of the computing units writes data, an access from the other computing unit is excluded. first and second computing units (2, 3) that execute control computation for controlling the operation of the vehicle; a memory diagnosis unit that diagnoses a shared storage area shared by the first and second computing units (2, 3); characterized by: an auxiliary storage unit that stores a copy of data stored in an area to be diagnosed, the area being diagnosed by the memory diagnosis unit; and an access destination setting unit that sets an access destination address in such a manner that while the memory diagnosis unit diagnoses the area to be diagnosed, the first and second computing units (2, 3) execute the control computation by using the copy stored in the auxiliary storage unit as an alternative to the data stored in the area to be diagnosed, wherein the vehicle control device includes a shared storage device having the shared storage area, the auxiliary storage unit is configured as an auxiliary storage area for storing the copy, and the vehicle control device further includes an auxiliary storage device that is a storage device different from the shared storage device, and that has the auxiliary storage area, wherein the auxiliary storage device is configured by a storage device having a reliability higher than a reliability of the shared storage device, and wherein the auxiliary storage device is configured as a storage device having a reliability higher than a reliability of the shared storage device by being configured as an exclusive storage device in which while one of the computing units writes data, an access from the other computing unit is excluded. an auxiliary storage unit that stores a copy of data stored in an area to be diagnosed, the area being diagnosed by the memory diagnosis unit; and an access destination setting unit that sets an access destination address in such a manner that while the memory diagnosis unit diagnoses the area to be diagnosed, the first and second computing units (2, 3) execute the control computation by using the copy stored in the auxiliary storage unit as an alternative to the data stored in the area to be diagnosed, wherein the vehicle control device includes a shared storage device having the shared storage area, the auxiliary storage unit is configured as an auxiliary storage area for storing the copy, and the vehicle control device further includes an auxiliary storage device that is a storage device different from the shared storage device, and that has the auxiliary storage area, wherein the auxiliary storage device is configured by a storage device having a reliability higher than a reliability of the shared storage device, and wherein the auxiliary storage device is configured as a storage device having a reliability higher than a reliability of the shared storage device by being configured as an exclusive storage device in which while one of the computing units writes data, an access from the other computing unit is excluded.