Background: The treatment of stomach neoplasm was determined by the identification on of invasion extent and perigastric lymph node through endoscopic ultrasonography (EUS). In this study, we investigated diagnostic accuracy of EUS examination before endoscopic submucosal dissection (ESD). Methods: A retrospective study was conducted to both EUS and ESD for stomach neoplasms that were performed at Seoul Paik Hospital between January 2006 and July 2015. We compared the accuracy of EUS according to the location of lesion, tumor size and ulcer presence or absence on lesion. Results: 49 patients were enrolled in this study; their mean age was 64.14 ± 11.33 years. There were 40 male (81.6%) and 9 female (18.4%) patients. The cases of confined to the mucosa on pathology finding were 41 (83.6%) and involved to submucosal layer(sm) 1 were 3 (6.1%) and sm2 were 2 (4%) and sm3 were 1 (2%) and proper muscle layer were 2 (4%). The cases of lymphatic invasion were 2 (4%). The sensitivity and accuracy of antrum were 91.6 % (95% CI: 0.81-1.03) and 83.3 % (95% CI: 0.70-0.97), body of stomach were 92.3 % (CI: 0.78-1.07) and 83.3% (CI: 0.66-1.00), respectively. Whether lesions were no significant differences in any location. The tumor size was divided by smaller than 20 mm group, 20-30 mm group and more than 30 mm group. The smaller than 20 mm group, 20-30 mm group and more than 30 mm group were 36, 9, 2 patients. The remaining 2 patients were not described. The sensitivity and accuracy of smaller than 20 mm group were 96.6 % (95% CI: 0.90-1.03) and 83.3 % (CI: 0.71-0.95) and 2-30 mm group were 66.7 % (CI: 0.29-1.04) and 77.8 % (CI: 0.51-1.04), respectively. All patients were divided by ulcer presence or not. 27 patients were ulcer presence and 22 patients were not. The sensitivity and accuracy of ulcer presence group were 77.3 % (CI : 0.60-0.95) and 74 % (CI : 0.57-0.90), ulcer absence group were 95 % (CI : 0.85-1.04) and 91 % (CI : 0.79-1.02). Conclusions: The EUS for stomach neoplasm was reliable of lesion without ulcerous finding, smaller than 20 mm in diameter and irrespective of stomach neoplasm location.