Methane thermal decomposition is a promising technology for producing CO₂-free hydrogen. This study experimentally examines how temperature (1,000–1,400^oC) and residence time affect methane decomposition in a ceramic tubular reactor. The results show that both the methane conversion rate and hydrogen yield increased with temperature, reaching approximately 95% and 45%, respectively, at 1,400^oC. At lower temperatures (1,000–1,200^oC), residence time had a significant impact, while at higher temperatures (1,300–1,400^oC), temperature became the predominant factor. Additionally, the formation of C₂ hydrocarbons, particularly acetylene (C₂H₂), increased as residence time decreased, negatively affecting both methane conversion and hydrogen yield. Analysis of the solid carbon by-products identified two distinct forms: amorphous, spherical carbon black particles and a semi-graphitic, crystalline carbon film. These findings provide essential data for optimizing the conditions of methane thermal decomposition.