Ultrasonography is highly sensitive for the diagnosis of sialoliths. Recently, wireless mobile ultrasonography was developed. We describe the case of a 49-year-old man who presented with painful postprandial left cheek swelling. Computed tomography detected a solitary 5-mm parotid duct stone with infection at the anterior portion of the left masseter muscle. Transoral stone removal was planned, although difficulty was expected in view of the surrounding infection. Surgery was performed under the guidance of mobile ultrasonography, and the stone was removed safely.