A 48-year-old Japanese female with left hypochondralgia presented at our hospital. Esophagogastroduodenoscopy (EGD) revealed gastric cancers and carpeting fundic gland polyposis (FGPs) without Helicobacter pylori infection. Computed tomography showed multiple liver metastases. Total colonoscopy revealed a colonic tubular adenoma but not polyposis. She was diagnosed as having advanced gastric cancer with liver metastasis and received chemotherapy. Her mother had died from gastric cancer, and her elderly brother and niece had FGPs as revealed by EGD. Thus, the pedigree was diagnosed as gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS). Germline mutation analysis exhibited a point mutation in exon1B of the APC gene (c.-191T > C). Adenocarcinoma showed a gastric mucinous phenotype and was positive for a somatic mutation of p53 , suggesting that p53 mutation may play a role in FGPs carcinogenesis. This is the first family with GAPPS in Asia in whom germline mutation of APC exon 1B has been detected.