Gastric antral vascular ectasia (GAVE) is known to be characterized by red patches or spots in a diffuse or linear array in the antrum of the stomach. The precise etiology of GAVE remains to be elucidated. Argon plasma laser coagulation (APC) has been used to control oozing from GAVE; however, there is no satisfactory long-term effect of APC in the control of oozing from GAVE. An acid reducer is used after APC because even physiological acid exposure might delay post-APC ulcer healing. We describe the case of a patient who had used an acid reducer and experienced repeated gastrointestinal hemorrhage due to GAVE. After ceasing to administer the acid reducer, incidences of hospitalization due to oozing from GAVE stopped. After the administration of the acid reducer was restarted, the patient had tarry stool, and diffuse oozing of blood was seen again. We report a first case of GAVE which was aggravated by acid reducer.