Scattering-type scanning near-field optical microscopy (s-SNOM) is a robust method for visualizing the optical response of surfaces with a spatial resolution down to 10 nm. Near-field signal detection relies on lock-in harmonic demodulation referring to tip oscillation driven by atomic force microscopy (AFM). The improvement of the spatial resolution requires stabilizing the sub-nanometer-scale tip-sample junction and improving the duty cycle of the near-field detection using a low tapping amplitude. However, both strategies are difficult to achieve with a conventional room-temperature setup based on tapping-mode AFM. In this study, 1-nm resolution s-SNOM is demonstrated based on noncontact-mode AFM using a quartz-tuning-fork sensor at a cryogenic temperature. The stable cantilever oscillation with an ultralow tip-oscillation amplitude allows for the sensitive detection of the near-field localized at the plasmonic Ag-tip–Ag-sample junction under visible laser illumination. With a Ag(111) sample partially covered by Si monolayer islands, we obtained s-SNOM images reflecting the material contrast between Si and Ag with 1-nm spatial resolution. The effective combination of noncontact-mode AFM, plasmonic cavity, and the elastic near-field detection has high potential for optical response imaging of photoactive detects and single molecules at atomic resolution.