Immune thrombocytopenia （ITP） is often accompanied by oral symptoms, and it is well know that one of the causes is Helicobactor pylori （H.pylori） infection. We report a case of acute ITP associated with H.pylori infection diagnosed with the appearance of multiple intraoral hematomas. The patient is 78-year-old woman who shows systemic petechial and multiple intraoral hematomas. Her platelet count was 0.3×10⁴/μl, and she was positive for anti-H.pylori antibody. She was treated immediately by intravenous administration of 20mg/day of methylprednisolone and 10g/day of immunoglobulin, and transfusion of 20 units of platelet concentrate. She was also treated for eradication of H.pylori. Her platelet count has recovered and her progress is good.