Background: Diabetes melitus is a degenerative disease which prevalence is increasing in developing country. Diabetes mellitus has some acute and chronic complications. Those affect blood vessels trough microvascular and macrovascular complications. In a state of chronic hyperglycemia, oxidative stress can occur. The condition affected endothelin-B (ETB) receptors in the heart organ. Objective: This research aimed to see the changes in the expression of ETB receptors on heart muscle and endothelial blood vessels of heart in a streptozotocin-induced diabetic rat model. Method: Rats were divided into two groups, one group as a control, and one group of diabetic rats model. Each group consist of 6 rats. Diabetic rat model obtained by streptozotocin injection dose 35mg/kgbw intra peritoneal to Sprague Dawley male rats aged 11-12 weeks. After 8 weeks of experiments, all the rats were terminated. The heart muscle was stained with immunohistochemical staining. Antibody of ETB was used to stain the heart muscle. Result: Imunohistochemical stain showed 18.32% ETB receptor in the heart muscle of control group and in 8.72% in diabetic group (p value = 0.001). Meanwhile, on endothelial blood vessels of heart there was 19.75% ETB receptor in control group and 10,39% ETB receptor in diabetic group (p value = 0.004). Conclusion: This study showed that the number of ETB receptors in heart muscle and endothelial blood vessels of the heart was reduced in diabetic group. Keywords: Diabetes Mellitus, Heart, Endothelin-B receptor, Streptozotocin