The aim of this study was to determine risk factors for prognosis in stage IV gastric cancer after gastrectomy. Surgical resection of stage IV gastric cancer has recently been proposed as the treatment of optimal choice; however treatment results, including prognosis, remain elusive. Patients included 128 resected patients of stage IV gastric cancer. The average survival time was 14.6 months with a 5-year survival rate of 4.7%. The most robust univariate predictors for poor prognosis were lymph node metastasis ratio (LNMR) over 50%, preoperative high value of CA19-9, preoperative high value of CEA and P factor as tumor factors, and LN dissection extent (LNDE) and operative curability as treatment factors. Among these univariate prognostic factors, LNMR, preoperative CA19-9 and P factor were independent on multivariate analysis (relative risk: RR = 1.71, 1.47 and 1.6, respectively), and the combination can clearly classify the patients into the definite prognostic groups as group A (0 factor, average survival 22.8 months), B (1 factor, 14.0 months), and C (more than 2 factors, 5.5 months). On the other hand, LNDE likely affects prognosis in all the 3 groups. Our results suggested that stage IV gastric cancer is subdivided into the definite prognostic group by tumor factors and rigorous surgical treatment might have the potential to prolong survival.