The 68-year-old man who have no particular symptom except 10 kg weight loss was received the gastroscopy as a part of diagnostic tests. On his gastroscopic examination, it was ascertained as high grade B-cell type mucosa- associated lymphoid tissue (MALT) lymphoma from the biopsy of the erosive lesion on the angle of stomach. This lesion, after pharmacotherapy for Helicobacter pylori, was visible the normal mucosal pattern at the gastroscopic follow-up. Hereupon the writer tried to review the clinical aspect, the diagnosis, the treatment, and the prognosis, along with the literature investigation regarding MA LT lymphoma.