Methane production from carbon dioxide and hydrogen is known as the Sabatier reaction. However, methanation process by the Sabatier reaction requires high temperatures and high pressures. Therefore, we tried to generate methane by mechanochemical method, using ball-milling as a new methanation process. As a result of ball milling for 3 hours at room temperature, generation of methane was observed. On the other hand, carbon dioxide was consumed more than expected. As for further verification, ball-milling was carried out for 6 hours under carbon dioxide atmosphere. EDX elemental analysis of the milled powder revealed significantly increased carbon content, suggesting the reaction of LaNi₅ surface with CO₂ followed by the formation of carbides or carbonates of La or Ni. A unique XRD profile was observed in the milled sample, yielding broad amorphous-like peak, possibly from La, and broad peak of Ni. It was shown that ball milling may cause phase separation into La and Ni not only in hydrogen atmosphere but also in carbon dioxide atmosphere.