Cellular Ca²⁺ signals have been proposed to activate signal for hormone secretion. In pancreatic β cell which produce insulin, Ca²⁺ signals have been known contributing insulin secretion. Prior to conduct this study, we confirmed Calbindin-D9k (CaBP-9k) which responsible for regulation of the distribution of free calcium in the cytoplasm. We confirmed Insulin-secreting β cell express CaBP-9k, and assumed that CaBP-9k play a certain role in β cell insulin synthesis or secretion. Using Calbindin-D9k knock out (CaBP-9k KO) mice, we demonstrate ablation of Calbindin-D9k (CaBP-9k) induces reduction of insulin secretion and hyperglycemia. Furthermore, to find the role of CaBP-9k in pathophysiologic condition, we gave hypoxic condition to wild-type and CaBP-9k KO mice for 10 days. Hypoxic condition induces endoplasmic reticulum (ER) stress, increase both insulin signaling and insulin resistance. By exposing hypoxia, CaBP-9k KO mice showed more increased level of ER stress marker protein than wild type mice. Thus, we assumed that CaBP-9k play a certain role in β cell insulin secretion, identifying ablation of CaBP-9k showed decreased level of Sulfonylurea receptor1 (SUR1) and ATP-sensitive K⁺ channel, an inward-rectifier potassium ion channel 6.2 (K_ir6.2). It demonstrated that CaBP-9k is part of the insulin-secreting calcium signaling which linked to K_ATP channel.