The detection of early gastric cancer is performed by endoscopic study with or without the dye-spraying method, which is useful in detecting small lesions or surface lesions. For the diagnosis of early gastric malignancy, magnification endoscopy, narrow-band imaging and optical coherence tomography are used for histological diagnosis and research. On the other hand, endoscopic ultrasonography is used to discuss the depth of carcinoma invasion, but cannot be used to detect the malignant lesions except for the rare cases of scirrhus-type gastric carcinoma, the histological results of which are sometimes difficult to obtain by biopsy study. The role of endoscopic ultrasonography diagnosis is to assist in making a decision of therapeutic strategy. Curative endoscopic treatment of early gastric cancer is common according to the development of various endoscopic techniques and accessories. Curative treatment is feasible using these techniques.