Carburizing process on low carbon stell can be done by using carburizer of corncob charcoal, pearl oyster shell powder. Cylindrical low carbon steel of AISI 1018 was used in the present study. The materials put inside the pack carburization with carburizer and pearl oyster shell powder. The pearl oyster shell powder varies of 5, 10, 20, and 25 weight percentage. The temperature of 910oC, 930oC, and 950oC was used to heat the materials with holding time of 90 and 150 minutes. Then, hardness Vickers test and microstructure test using scanning electron microscope (SEM) was used to analyze the hardness number of each materials. The results shown that the hardnessnumber increased up to 262,47 kg/mm2 (82 %) from 144,08 kg/mm by adding 20 % weight of pearl oyster shell powder with heating and holding time of 950oC and 150 minutes, respectively. From microstructure and composition test reveal that surface hardening occurred on the low carbon steel surface due to carbon diffusion during pack carburizing process.