We fabricated a novel sensor array chip that enables simple, rapid, and sequence-specific DNA detection without any process to label DNAs or any external electrochemical indicators. We found the conditions for the cleaning of electrode surfaces and the preparation of DNA sensor array chips. A long-term storage for several weeks inactivated photolithographically fabricated 384-ch microelectrode array chips before surface modification. We revealed that the treatments with O2 plasma and acidic solutions reactivated the long-term stored chips, and demonstrated that the DNA sensor arrays prepared from the reactivated chips detected DNAs sequence-specifically, similarly to freshly fabricated sensors. We found that feasible DNA sensor array chips can be prepared from the electrode array chips stored even for a long period, as long as the stored chips are treated before use with O2 plasma and acid solutions under optimized conditions.