Erythropoiesis-stimulating agent (ESA) has been recognized as an effective way in the treatment of anemia due to chronic kidney disease, but we sometimes see intractable hemodialysis (HD) patients. The causes of ESA-resistant anemia in HD patients include deficiency of trace elements. We report the case of an 89-year-old male who developed pancytopenia after taking an excessive amount of zinc formulation for ESA-resistant anemia during maintenance dialysis. He was prescribed zinc acetate hydrate formulation about 6 months before his presentation. He was found to have pancytopenia 1 month before his presentation, at which point he was introduced to our hospital. We suspected a copper deficiency at the first visit and stopped zinc and added copper, and his condition subsequently improved without being handicapped. Zinc antagonizes copper, so we must take care to diagnose patients ingesting zinc supplements.