The authors have proposed traveling wave type wall climbing robot simulating the snail moving method. This robot is composed of a plurality of units, each of which is adsorbed. Since units are connected by a universal joint, they correspond to curved surfaces. Proceed by propagating expansion and contraction between units when proceeding. In this study, we develop a negative pressure adsorption type traveling wave type wall moving robot capable of traveling on a nonmagnetic surface such as an airplane surface. As a friction switching method necessary for progression, we propose a friction switching method by opening and closing the gap. The usefulness of the friction switching method by opening and closing the gap is shown.