Introduction: Bone defect is one of the most common problems encountered in the alveolar bone. Osteoblast is an important component in the bone healing process. Osteoblast cell plays an important role in bone matrix synthesis and bone matrix mineralization. Synthetic hydroxyapatite is biocompatible, osteoconductive and able to merge with bone well. The eggshell has a high calcium carbonate so that it can be used as a source of hydroxyapatite synthesis. Methods: Laboratory experimental with in vivo true experimental design and Randomized Post Test Only Controlled Group Design method on male Wistar rat. The samples were divided as the Negative Control (C-) group (the group that was not given bone defect nor eggshell powder), the Experimental 1 (E1) group (the group that was given bone defect but not given eggshell powder), and the Experimental 2 (E2) group (the group that was given bone defect and eggshell powder). The eggshell powder was given in 42 days. On the 43th day, the rats were euthanized. The histological preparations from the mandibular bone of male Wistar rats were stained with Hematoxylin-Eosin stain- ing. The observation and calculation of the number of osteoblasts were done under microscope with 1000x mag- nification. Results: The ANOVA test result showed a significant increase of the number of osteoblast cell in the E2 group (p<0,05). The Post-Hoc test results shows a significant difference between E1 and E2 group. Conclusion: The administration of chicken eggshell powder can affect the number of osteoblast cell in the mandibular bone healing of male Wistar rat.