The possibility of employing endoscopic laser therapy (ELT) to cure early gastric cancer is discussed from the viewpoint of using endoscopic ultrasonography (EUS). Using EUS the digestive tract wall was seen as a 5-layered structure corresponding to the histological layers. On the basis of this layered structure of the gastric wall, the depth of cancer invasion and the results of laser treatment were evaluated. In 128 cases of gastric cancer examined by EUS and confirmed histologically, when the depth of cancer invasion was classified as mucosal, submucosal, muscularis propria, and deeper-than-subserosal invasion, the accuracy rate was 80%. In 26 cases of early gastric cancer, in the EUS images of the lesions before and after ELT, a lack of the gastric wall caused by the laser irradiation was observed. Furthermore, in the long-term follow-up study using EUS, the residual growth of the extraluminal cancer was detectable. EUS is one of the most promising methods for the evaluation of curative laser treatment of early gastric cancer.