The present invention prepared insulin-producing endocrine cells by inducing the differentiation of human embryonic stem cells or human induced pluripotent stem cells into definitive endoderm (DE), pancreatic endoderm (PE), endocrine progenitors (EP), and endocrine cells (EC) stepwise in that order. Particularly, the present invention established the conditions for the formation of an insulin producing endocrine aggregate (EA) from the endocrine cells. Especially in this invention, it was confirmed that the endocrine aggregate has the cell proliferation potential at a significant level and has the increased insulin productivity as well as the activity of inhibiting cell necrosis and apoptosis. Therefore, the method for preparing the endocrine aggregate of insulin-producing beta cells from human pluripotent stem cells can be effectively used for the examination of the medicinal effect of the conventional antidiabetic agents and of the novel antidiabetic drugs.