A 63-year-old woman who presented with chest and back pain underwent an upper gastrointestinal endoscopy which revealed elevated legion in the antrum mucosa. Histologic examinations of gastric biopsies were showing monoclonal proliferation plasma cells containing Russell bodies. Differential diagnosis from B-cell lymphoma and plasmacytoma is difficult, because of monoclonality. Molecular analyses of immunoglobulin heavy chain (IgH) gene demonstrated that gene rearrangement was negative. Thus, diagnosis of Russell body gastritis was made. The Giemsa stains were also showing infection of Helicobacter pylori (H.pylori). After eradication therapy for H.pylori, follow-up upper gastrointestinal endoscopy was performed. She then recovered.