This invention proposes a disk array apparatus capable of improving its reliability. This disk array apparatus includes a first controller, and a second controller configured redundantly with the first controller, wherein the first controller and the second controller respectively include a storage area for storing firmware and are both in an operating state. When update processing of an update portion as a portion to be updated in the firmware of the first controller is unsuccessful, the first controller confirms whether update processing of an update portion of the firmware of the second controller is also unsuccessful, and, in a case where the update processing of the update portion of the firmware of the second controller has ended normally, rewrites firmware data of the update portion of the first controller with the firmware data of the update portion of the second controller.