Two-dimensional (2D) superconductors are known to undergo transition into insulator by the application of magnetic fields and/or the introduction of disorder even at zero temperature. Recent studies using highly crystalline 2D superconductors revealed various unique quantum phases such as quantum metallic phase and quantum Griffiths phase near the transition. Microscopic understandings on these curious phases are, however, not sufficient yet. In order to elucidate them microscopically. We investigated superconductivity of Pb striped-incommensurate (SIC) phase, one of the stable mono-layer superconducting phases using scanning tunneling microscopy (STM). Since we formed the ultimately-thin superconductor on various vicinal substrates, high density of steps, which work as a disorder and a Josephson coupling, was introduced into the superconductor. Through the observation of vortices under out-of-plane magnetic field we investigated the role of high density steps or disorder on their superconductivity.1)