The gasification technology for biomass conversion has a limitation for some applications, including engines and turbines, because it produces tar-containing gas. In this study, a gliding arc plasma reformer was developed to remove tar. The plasma discharge in the gliding-type reformer is based on the both non-equilibrium and equilibrium plasmas. A simulation test was conducted using anthracene, which is produced during the gasification of biomass and waste, as the representative tar substance. In the optimal condition, the anthracene decomposition efficiency was 96.1%, and the energy efficiency was 1.14 g/kWh. The higher heating value of the gas produced from the anthracene decomposition was 11,324 kJ/Nm3, and the carbon balance was 98%. The steam flow rate, power input, total gas flow rate, and input concentration change were used as variables for the test. The anthracene decomposition efficiency was 81% when the gliding arc plasma reformer was used. When steam was fed at a rate of 0.63 L/min, the decomposition efficiency was highest (96.1%) due to the creation of OH radicals. The energy efficiency was highest (2.63 g/kWh) when the total gas flow rate was 24.1 L/min. H2, CO, and CO2 were produced as reformed gases. At the steam injection rate of 0.37 L/min or more, carbon black did not appear. Thus, it was verified that the gliding arc plasma reformer is effective for tar reduction.