To clarify the components of the thickened gastric wall in acute gastric anisakiasis, we evaluated endoscopic ultrasonography (EUS) findings of acute gastric anisakiasis. Ten patients with acute gastric anisakiasis underwent endoscopic ultrasonography immediately after anisakiasis was diagnosed by endoscopy. In the acute phase of gastric anisakiasis, endoscopic ultrasonography (EUS) detected a thickening of the gastric wall made of mainly thickened third layer with low echoic changes. When EUS was performed 7 to 11 days later in seven patients, the EUS findings had normalized. We made clear EUS findings in acute gastritis due to gastric anisakiasis. Consequently, we found, by EUS, that the main inflammatory lesion in anisakiasis was in the submucosal layer of gastric wall.