We report rare cases of internal hernia after surgery for gastric cancer. Four patients who had undergone gastrectomy (Roux-en Y reconstruction) for gastric cancer were admitted to our hospital after onset of abdominal pain or vomiting. Abdominal X-ray revealed small intestine gas and niveau, and abdominal CT scan showed the whirl sign in all cases. We diagnosed internal hernia and performed surgery. In 3 cases, small intestine was strangulated through the space between the mesentery of the Roux-Limb and transverse mesocolon, and in one case, it was strangulated through the space between the mesentery of the Roux-Limb and the mesentery of afferent loop. We reversed the ileal strangulation and closed the hernia orifice.