To halt the pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), governments around the world have imposed policies, such as lockdowns, mandatory mask wearing, and social distancing. The application of disinfecting materials in shared public facilities can be an additional measure to control the spread of the virus. Copper is a prominent material with antibacterial and antiviral effects. In this study, we synthesized copper nanoparticles (CuNPs) as a surface coating agent and assessed their antiviral activity against SARS-CoV-2. CuNPs with a mean size of 254 nm in diameter were synthesized from copper sulfate as a source and were predominantly composed of copper oxide. The synthesized CuNPs were mixed with resin-based paint (CuNP/paint) and sprayed on the surface of stainless steel remnants. SARS-CoV-2 lost 97.8% infectivity on the CuNP/paint-coated surface after 30 min of exposure and more than 99.995% infectivity after 1 h of exposure. The inactivation rate was approximately 36-fold faster than that on the paint alone-coated and uncoated surfaces. The CuNP/paint-coated surface showed powerful inactivation of SARS-CoV-2 infectivity, although further study is needed to elucidate the inactivation mechanisms. Applications of CuNP/paint coatings to public or hospital facilities and other commonly touched areas are expected to be beneficial.